Method and system for instruction of a computer using processing sensor

ABSTRACT

The present invention provides a method for enabling instruction of a computer to perform tasks, the method including the steps of: providing a user with at least one form printable on a surface to provide one or more first viewable information zones relating to one or more available commands and one or more second viewable information zones relating to one or more objects; receiving, in a computer system, indicating data from a sensing device operated by the user regarding movement of the sensing device relative to the surface, said movement including a stroke of part of the sensing device on or relative to said surface; determining, in the computer system and from the indicating data, if the stroke substantially links one or more of said first viewable information zones with one or more of said second viewable information zones, and thereby interpreting the stroke as designating (i) a respective one or more of said available commands and (ii) a respective one or more of said objects; and applying in the computer system the designated one or more of said available commands to the designated one or more of said objects.

Various methods, systems end apparatus relating to the present inventionare disclosed in the following co-pending applications/granted patentsfiled by the applicant or assignee of the present invention with thepresent application Sep. 15, 2000:

6,679,420, 09/669,599, 6,720,985,

The disclosures of these co-pending applications are incorporated hereinby cross-reference.

Various methods, systems and apparatus relating to the present inventionare disclosed in the following co-pending applications/granted patentsfiled by the applicant or assignee of the present invention a with thepresent application on Jun. 30, 2000:

09/609,139, 9/608,970, 6,678,499, 09/607,852 09/607,656, 09/609,132,09/609,303, 09/610,095, 9/609,596, 09/607,843, 09/607,605, 9/608,178,09/609,553, 09/609,233, 9/609,149, 09/608,022, 09/609,232, 9/607,844,6,457,883, 9/608,920, 09/607,985, 6,398,332, 6,394,573, 6,622,923

The disclosures of these co-pending applications arc incorporated hereinby cross-reference.

Various methods, systems and apparatus relating to the present inventionare disclosed in the following co-pending applications filed by theapplicant or assignee of the present invention on 23 May 2000:

09/575,197, 09/575,195, 09/575,159, 09/575,132, 09/575,123, 09/575,148,09/575,130, 09/575,165, 09/575,153, 09/575,118, 09/575,131, 09/575,116,09/575,144, 09/575,139, 09/575,186, 6,681,045, 6,728,000, 09/575,145,09/575,192, 09/575,181, 09/575,193, 09/575,156, 09/575,183, 09/575,160,09/575,150, 09/575,169, 6,644,642, 6,502,614, 6,622,999, 6,669,385,6,549,935, 09/575,187, 6,727,996, 6,591,884, 6,439,706, 09/575,196,09/575,198, 6,290,349, 6,428,155, 09/575,146, 09/575,174, 09/575,163,6,737,591, 09/575,154, 09/575,129, 09/575,124, 09/575,188, 09/575,189,09/575,162, 09/575,172, 09/575,170, 09/575,171, 09/575,161, 6,428,133,6,526,658, 6,315,399, 6,338,548, 6,540,319, 6,328,431, 6,328,425,09/575,127, 6,383,833, 6,464,332, 6,390,591, 09/575,152, 6,328,417,6,409,323, 6,281,912, 6,604,810, 6,318,920, 6,488,422, 09/575,108,09/575,109, 09/575,110,

The disclosures of these co-pending applications are incorporated hereinby cross-reference.

FIELD OF INVENTION

The present invention relates generally to computing systems and, moreparticularly, to a method and system for enabling instruction of acomputer to perform tasks. It has specific application to the operationof a computer system involving a form-based user interface.

BACKGROUND

The advent of graphical user interfaces for computer systems generatedan alternative method for instructing a computer system to performdesired tasks. In particular, the development of the mouse and thegraphical representation of objects on computer screens enabled users toselect an object by placing the mouse cursor over the object, or in thevicinity thereof, and activating a button or other selection means onthe mouse.

The selection of objects represented in a graphical format enabled auser to instruct a computer to perform tasks with respect to thatobject. An example of this approach is the deletion of a document fromthe computer, which in some systems could be effected by selecting thegraphical representation of the object to be deleted and then selectinga graphical representation of a “delete” command. This approach couldalso be used for the association of attributes with objects.

An alternative approach for instructing a computer to perform the taskof deleting an object was to select the graphical representation of theobject and to move the object, generally referred to as “dragging” theobject, into the vicinity of a graphical representation of a commandthat would execute the desired task. A particular example of this wasthe use of a graphical representation of a garbage can or trash can torepresent the “delete” command. Thus, users could remove objects fromthe computer system by selecting and “dragging” the object into thevicinity of the garbage can. Once in the vicinity of the graphicalrepresentation of the command, users could activate that command byplacing the object onto the represented command, generally referred toas “dropping” the object.

The graphical user interface assisted users wishing to associateattributes with objects. This could be effected by selecting thegraphical representation of an attribute and then selecting thegraphical representation of the object to which the attribute shouldapply. Alternatively, the user could select the graphical representationof the object, or attribute, and drag it into the vicinity of thegraphical representation of the attribute or object and drop it, thusforming the desired association between the object and the attribute.

Additionally, the use of such a graphical user interface enabled usersto relatively easily associate objects with one another. For example,when sending an electronic mail message, users often wish to attach anobject to that message generally in the form of a document or picturethat is relevant to the content of the mail message. In such acircumstance, the user is effectively associating two objects with oneanother, namely, the document or picture and the electronic mailmessage.

SUMMARY OF INVENTION

It is an objective of the present invention to provide a method andsystem for enabling instruction of a computer to perform tasks.

The invention provides in one aspect a method for enabling instructionof a computer to perform tasks, the method including the steps of:

providing a user with at least one form printable on a surface toprovide one or more first viewable information zones relating to one ormore available commands and one or more second viewable informationzones relating to one or more objects;

receiving, in a computer system, indicating data from a sensing deviceoperated by the user regarding movement of the sensing device relativeto the surface, said movement including a stroke of part of the sensingdevice on or relative to said surface;

interpreting, in the computer system and from the indicating data, ifthe stroke substantially links one or more of said first viewableinformation zones with one or more of said second viewable informationzones, and thereby interpreting the stroke as designating (i) arespective one or more of said available commands and (ii) a respectiveone or more of said objects; and

applying in the computer system the designated one or more of saidavailable commands to the designated one or more of said objects.

The invention provides in a further aspect a system for enablinginstruction of a computer to perform tasks, the system including:

at least one form printable on a surface to provide one or more firstviewable information zones relating to one or more available commandsand one or more second viewable information zones relating to one ormore objects;

a computer system for receiving indicating data from a sensing deviceoperated by a user regarding movement of the sensing device relative tothe surface, said movement including a stroke of part of the sensingdevice on or relative to said surface,

the computer system adapted to determine, from the indicating datareceived, if the sensing device stroke substantially links one or moreof said first viewable information zones with one or more of said secondviewable information zones and thereby designates (i) a respective oneor more of said available commands and (ii) a respective one or more ofsaid objects one or more of said available commands,

the computer system adapted to apply the designated one or more of saidavailable commands to the designated one or more of said objects.

In applying the invention, the at least one form may include coded dataindicative of at least one reference point of the form, by means ofwhich the indicating data can be generated. Additionally, the coded datamay be indicative of the form's identity. In an alternative form, thesensing device may generate the indicating data independently of theform, by use of, for example, accelerometers incorporated into thesensing device, or by an optical mouse technique. A suitable manner ofstroke may be prescribed for designating objects/commands, such ascircumscription, or image border intersection. In a preferred form ofassociation of an object with a command zone, the latter represented as,say, a command button or icon, a single stroke designating an object andextending to meet the command button or icon, or vica versa, will causeor permit the related command to be effected in respect of thedesignated object.

Clearly an object may signify any data set storable by the computersystem, representing, for example, an image or part of an image, a textitem, a computer file, a message, etc.

A command may be any command available to be effected by the computersystem. For example, it may relate to cutting, copying, deleting orpasting an object. It may relate to applying an attribute to an object,such as a colour, texture, shading, border, etc. to an image object, ora size, font, style, effect, etc. to a text object.

Accordingly, the present invention provides a system and a method whichutilizes one or more forms capable of interacting with a computer systemWhilst the novel method and system of the present invention may be usedin conjunction with a single computer system, in a particularlypreferred form it is designed to operate over a computer network, suchas the Internet.

Physically, the form is disposed on a surface medium which may be of anysuitable structure. However, in a preferred embodiment, the form isdisposed on sheet material such as paper or the like which has the codeddata printed on it and which allows interaction with the computersystem. The coded data is detectable preferably, but not exclusively,outside the visible spectrum, thereby enabling it to be machine-readablebut substantially invisible to the human eye. The form may also includevisible material which provides information to a user, such as theapplication or purpose of the form, and which visible information may beregistered or correlate in position with the relevant hidden coded data.

The system also includes a sensing device to convey data from the formto the computer system, and in some instances, to contribute additionaldata. Again, the sensing device may take a variety of forms but ispreferably compact and easily portable. In a particularly preferredarrangement, the sensing device is configured as a pen which is designedto be able to physically mark the interactive form as well as toselectively enable the coded data from the form to be read andtransmitted to the computer system. The coded data then provides controlinformation, configured such that designation thereof by a user causesinstructions to be applied to the software running on the computersystem or network.

The nature of the interaction between the form and the sensing deviceand the data that each contributes to the computer system may vary. Inone arrangement, the coded data on the form is indicative of theidentity of the form and of at least one reference point on that form.In another embodiment, the interactive form includes coded data which isindicative of a parameter of the form, whereas the sensing device isoperative to provide data regarding its own movement relative to thatform to the computer system together with coded data from the form. Inyet another arrangement, the form includes the coded data which at leastidentifies the form, and the sensing device is designed to provide, tothe computer system, data based on the form coded data, and also on datawhich identifies the user of the device.

In a preferred arrangement, the system and method also employs speciallydesigned printers to print the interactive form. Further these printersconstitute or form part of the computer system and are designed toreceive data from the sensing device. As indicated above, the system andmethod of the invention is ideally suited to operate over a network. Inthis arrangement, the printers are fully integrated into the network andallow for printing of the interactive forms on demand and also fordistributing of the forms using a mixture of multicast and pointcastcommunication protocols.

Accordingly, in a preferred form, the present invention provides methodsand systems which use a paper and pen based interface for a computersystem. This provides many significant benefits over traditionalcomputer systems. The advantage of paper is that it is widely used todisplay and record information. Further, printed information is easierto read than information displayed on a computer screen. Moreover, paperdoes not run on batteries, can be read in bright light, or robustlyaccepts coffee spills or the like and is portable and disposable.Furthermore, the system allows for hand-drawing and hand-writing to becaptured which affords greater richness of expression than input via acomputer keyboard and mouse.

BRIEF DESCRIPTION OF DRAWINGS

Preferred and other embodiments of the invention will now be described,by way of non-limiting example only, with reference to the accompanyingdrawings, in which:

FIG. 1 is a schematic of a the relationship between a sample printednetpage and its online page description;

FIG. 2 is a schematic view of a interaction between a netpage pen, anetpage printer, a netpage page server, and a netpage applicationserver;

FIG. 3 illustrates a collection of netpage servers and printersinterconnected via a network;

FIG. 4 is a schematic view of a high-level structure of a printednetpage and its online page description;

FIG. 5 a is a plan view showing a structure of a netpage tag;

FIG. 5 b is a plan view showing a relationship between a set of the tagsshown in FIG. 5 a and a field of view of a netpage sensing device in theform of a netpage pen;

FIG. 6 a is a plan view showing an alternative structure of a netpagetag;

FIG. 6 b is a plan view showing a relationship between a set of the tagsshown in FIG. 6 a and a field of view of a netpage sensing device in theform of a netpage pen;

FIG. 6 c is a plan view showing an arrangement of nine of the tags shownin FIG. 6 a where targets are shared between adjacent tags;

FIG. 6 d is a plan view showing the interleaving and rotation of thesymbols of the four codewords of the tag shown in FIG. 6 a;

FIG. 7 is a flowchart of a tag image processing and decoding algorithm;

FIG. 8 is a perspective view of a netpage pen and its associatedtag-sensing field-of-view cone;

FIG. 9 is a perspective exploded view of the netpage pen shown in FIG.8;

FIG. 10 is a schematic block diagram of a pen controller for the netpagepen shown in FIGS. 8 and 9;

FIG. 11 is a perspective view of a wall-mounted netpage printer;

FIG. 12 is a section through the length of the netpage printer of FIG.11;

FIG. 12 a is an enlarged portion of FIG. 12 showing a section of theduplexed print engines and glue wheel assembly;

FIG. 13 is a detailed view of the ink cartridge, ink, air and gluepaths, and print engines of the netpage printer of FIGS. 11 and 12;

FIG. 14 is a schematic block diagram of a printer controller for thenetpage printer shown in FIGS. 11 and 12;

FIG. 15 is a schematic block diagram of duplexed print enginecontrollers and Memjet™ printheads associated with the printercontroller shown in FIG. 14;

FIG. 16 is a schematic block diagram of the print engine controllershown in FIGS. 14 and 15;

FIG. 17 is a perspective view of a single Memjet™ printing element, asused in, for example, the netpage printer of FIGS. 10 to 12;

FIG. 18 is a perspective view of a small part of an array of Memjet™printing elements;

FIG. 19 is a series of perspective views illustrating the operatingcycle of the Memjet™ printing element shown in FIG. 13;

FIG. 20 is a perspective view of a short segment of a pagewidth Memjet™printhead;

FIG. 21 is a schematic view of a user class diagram;

FIG. 22 is a schematic view of a printer class diagram;

FIG. 23 is a schematic view of a pen class diagram;

FIG. 24 is a schematic view of an application class diagram;

FIG. 25 is a schematic view of a document and page description classdiagram;

FIG. 26 is a schematic view of a document and page ownership classdiagram;

FIG. 27 is a schematic view of a terminal element specialization classdiagram;

FIG. 28 is a schematic view of a static element specialization classdiagram;

FIG. 29 is a schematic view of a hyperlink element class diagram;

FIG. 30 is a schematic view of a hyperlink element specialization classdiagram;

FIG. 31 is a schematic view of a hyperlinked group class diagram;

FIG. 32 is a schematic view of a form class diagram;

FIG. 33 is a schematic view of a digital ink class diagram;

FIG. 34 is a schematic view of a field element specialization classdiagram;

FIG. 35 is a schematic view of a checkbox field class diagram;

FIG. 36 is a schematic view of a text field class diagram;

FIG. 37 is a schematic view of a signature field class diagram;

FIG. 38 is a flowchart of an input processing algorithm;

FIG. 38 a is a detailed flowchart of one step of the flowchart of FIG.38;

FIG. 39 is a schematic view of a page server command element classdiagram;

FIG. 40 is a schematic view of a subscription delivery protocol;

FIG. 41 is a schematic view of a hyperlink request class diagram;

FIG. 42 is a schematic view of a hyperlink activation protocol;

FIG. 43 is a schematic view of a form submission protocol;

FIG. 44 is a schematic view of a set of user interface flow documenticons;

FIG. 45 is a schematic view of a set of user interface page layoutelement icons;

FIG. 46 is an illustration of various strokes which can be used to applyattributes or commands from a palette or menu to one or more objects orobject features;

FIG. 47 is a schematic view of a draggable hyperlink class diagram;

FIG. 48 is a schematic view of an article group class diagram;

FIG. 49 is a schematic view of a selection hyperlink class diagram;

FIG. 50 is a schematic view of a selection page server command classdiagram;

FIG. 51 is a schematic view of a selection retrieval protocol;

FIG. 52 is a schematic view of a photo album page composition userinterface flow; and

FIG. 53 is a schematic view of a photo album page composition form.

DETAILED DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

Note: Memjet™ is a trade mark of Silverbrook Research Pty Ltd,Australia.

In the preferred embodiment, the invention is configured to work withthe netpage networked computer system, a detailed overview of whichfollows. It will be appreciated that not every implementation willnecessarily embody all or even most of the specific details andextensions discussed below in relation to the basic system. However, thesystem is described in its most complete form to reduce the need forexternal reference when attempting to understand the context in whichthe preferred embodiments and aspects of the present invention operate.

In brief summary, the preferred form of the netpage system employs acomputer interface in the form of a mapped surface, that is, a physicalsurface which contains references to a map of the surface maintained ina computer system. The map references can be queried by an appropriatesensing device. Depending upon the specific implementation, the mapreferences may be encoded visibly or invisibly, and defined in such away that a local query on the mapped surface yields an unambiguous mapreference both within the map and among different maps. The computersystem can contain information about features on the mapped surface, andsuch information can be retrieved based on map references supplied by asensing device used with the mapped surface. The information thusretrieved can take the form of actions which are initiated by thecomputer system on behalf of the operator in response to the operator'sinteraction with the surface features.

In its preferred form, the netpage system relies on the production of,and human interaction with, netpages. These are pages of text, graphicsand images printed on ordinary paper, but which work like interactiveweb pages. Information is encoded on each page using ink which issubstantially invisible to the unaided human eye. The ink, however, andthereby the coded data, can be sensed by an optically imaging pen andtransmitted to the netpage system.

In the preferred form, active buttons and hyperlinks on each page can beclicked with the pen to request information from the network or tosignal preferences to a network server. In one embodiment, text writtenby hand on a netpage is automatically recognized and converted tocomputer text in the netpage system, allowing forms to be filled in. Inother embodiments, signatures recorded on a netpage are automaticallyverified, allowing e-commerce transactions to be securely authorized.

As illustrated in FIG. 1, a printed netpage 1 can represent ainteractive form which can be filled in by the user both physically, onthe printed page, and “electronically”, via communication between thepen and the netpage system. The example shows a “Request” formcontaining name and address fields and a submit button. The netpageconsists of graphic data 2 printed using visible ink, and coded data 3printed as a collection of tags 4 using invisible ink. The correspondingpage description 5, stored on the netpage network, describes theindividual elements of the netpage. In particular it describes the typeand spatial extent (zone) of each interactive element (i.e. text fieldor button in the example), to allow the netpage system to correctlyinterpret input via the netpage. The submit button 6, for example, has azone 7 which corresponds to the spatial extent of the correspondinggraphic 8.

As illustrated in FIG. 2, the netpage pen 101, a preferred form of whichis shown in FIGS. 8 and 9 and described in more detail below, works inconjunction with a netpage printer 601, an Internet-connected printingappliance for home, office or mobile use. The pen is wireless andcommunicates securely with the netpage printer via a short-range radiolink 9.

The netpage printer 601, a preferred form of which is shown in FIGS. 11to 13 and described in more detail below, is able to deliver,periodically or on demand, personalized newspapers, magazines, catalogs,brochures and other publications, all printed at high quality asinteractive netpages. Unlike a personal computer, the netpage printer isan appliance which can be, for example, wall-mounted adjacent to an areawhere the morning news is first consumed, such as in a user's kitchen,near a breakfast table, or near the household's point of departure forthe day. It also comes in tabletop, desktop, portable and miniatureversions.

Netpages printed at their point of consumption combine the ease-of-useof paper with the timeliness and interactivity of an interactive medium.

As shown in FIG. 2, the netpage pen 101 interacts with the coded data ona printed netpage 1 and communicates, via a short-range radio link 9,the interaction to a netpage printer. The printer 601 sends theinteraction to the relevant netpage page server 10 for interpretation.In appropriate circumstances, the page server sends a correspondingmessage to application computer software running on a netpageapplication server 13. The application server may in turn send aresponse which is printed on the originating printer.

The netpage system is made considerably more convenient in the preferredembodiment by being used in conjunction with high-speedmicroelectromechanical system (MEMS) based inkjet (Memjet™) printers. Inthe preferred form of this technology, relatively high-speed andhigh-quality printing is made more affordable to consumers. In itspreferred form, a netpage publication has the physical characteristicsof a traditional newsmagazine, such as a set of letter-size glossy pagesprinted in full color on both sides, bound together for easy navigationand comfortable handling.

The netpage printer exploits the growing availability of broadbandInternet access. Cable service is available to 95% of households in theUnited States, and cable modem service offering broadband Internetaccess is already available to 20% of these. The netpage printer canalso operate with slower connections, but with longer delivery times andlower image quality. Indeed, the netpage system can be enabled usingexisting consumer inkjet and laser printers, although the system willoperate more slowly and will therefore be less acceptable from aconsumer's point of view. In other embodiments, the netpage system ishosted on a private intranet. In still other embodiments, the netpagesystem is hosted on a single computer or computer-enabled device, suchas a printer.

Netpage publication servers 14 on the netpage network are configured todeliver print-quality publications to netpage printers. Periodicalpublications are delivered automatically to subscribing netpage printersvia pointcasting and multicasting Internet protocols. Personalizedpublications are filtered and formatted according to individual userprofiles.

A netpage printer can be configured to support any number of pens, and apen can work with any number of netpage printers. In the preferredimplementation, each netpage pen has a unique identifier. A householdmay have a collection of colored netpage pens, one assigned to eachmember of the family. This allows each user to maintain a distinctprofile with respect to a netpage publication server or applicationserver.

A netpage pen can also be registered with a netpage registration server1 and linked to one or more payment card accounts. This allowse-commerce payments to be securely authorized using the netpage pen. Thenetpage registration server compares the signature captured by thenetpage pen with a previously registered signature, allowing it toauthenticate the user's identity to an e-commerce server. Otherbiometrics can also be used to verify identity. A version of the netpagepen includes fingerprint scanning, verified in a similar way by thenetpage registration server.

Although a netpage printer may deliver periodicals such as the morningnewspaper without user intervention, it can be configured never todeliver unsolicited junk mail. In its preferred form, it only deliversperiodicals from subscribed or otherwise authorized sources. In thisrespect, the netpage printer is unlike a fax machine or e-mail accountwhich is visible to any junk mailer who knows the telephone number ore-mail address.

1 Netpage System Architecture

Each object model in the system is described using a Unified ModelingLanguage (UML) class diagram. A class diagram consists of a set ofobject classes connected by relationships, and two kinds ofrelationships are of interest here: associations and generalizations. Anassociation represents some kind of relationship between objects, i.e.between instances of classes. A generalization relates actual classes,and can be understood in the following way: if a class is thought of asthe set of all objects of that class, and class A is a generalization ofclass B, then B is simply a subset of A. The UML does not directlysupport second-order modelling—i.e. classes of classes.

Each class is drawn as a rectangle labelled with the name of the class.It contains a list of the attributes of the class, separated from thename by a horizontal line, and a list of the operations of the class,separated from the attribute list by a horizontal line. In the classdiagrams which follow, however, operations are never modelled.

An association is drawn as a line joining two classes, optionallylabelled at either end with the multiplicity of the association. Thedefault multiplicity is one. An asterisk (*) indicates a multiplicity of“many”, i.e. zero or more. Each association is optionally labelled withits name, and is also optionally labelled at either end with the role ofthe corresponding class. An open diamond indicates an aggregationassociation (“is-part-of”), and is drawn at the aggregator end of theassociation line.

A generalization relationship (“is-a”) is drawn as a solid line joiningtwo classes, with an arrow (in the form of an open triangle) at thegeneralization end.

When a class diagram is broken up into multiple diagrams, any classwhich is duplicated is shown with a dashed outline in all but the maindiagram which defines it. It is shown with attributes only where it isdefined.

1.1 Netpages

Netpages are the foundation on which a netpage network is built. Theyprovide a paper-based user interface to published information andinteractive services.

A netpage consists of a printed page (or other surface region) invisiblytagged with references to an online description of the page. The onlinepage description is maintained persistently by a netpage page server.The page description describes the visible layout and content of thepage, including text, graphics and images. It also describes the inputelements on the page, including buttons, hyperlinks, and input fields. Anetpage allows markings made with a netpage pen on its surface to besimultaneously captured and processed by the netpage system.

Multiple netpages can share the same page description. However, to allowinput through otherwise identical pages to be distinguished, eachnetpage is assigned a unique page identifier. This page ID hassufficient precision to distinguish between a very large number ofnetpages.

Each reference to the page description is encoded in a printed tag. Thetag identifies the unique page on which it appears, and therebyindirectly identifies the page description. The tag also identifies itsown position on the page. Characteristics of the tags are described inmore detail below.

Tags are printed in infrared-absorptive ink on any substrate which isinfrared-reflective, such as ordinary paper. Near-infrared wavelengthsare invisible to the human eye but are easily sensed by a solid-stateimage sensor with an appropriate filter.

A tag is sensed by an area image sensor in the netpage pen, and the tagdata is transmitted to the netpage system via the nearest netpageprinter. The pen is wireless and communicates with the netpage printervia a short-range radio link. Tags are sufficiently small and denselyarranged that the pen can reliably image at least one tag even on asingle click on the page. It is important that the pen recognize thepage ID and position on every interaction with the page, since theinteraction is stateless. Tags are error-correctably encoded to makethem partially tolerant to surface damage.

The netpage page server maintains a unique page instance for eachprinted netpage, allowing it to maintain a distinct set of user-suppliedvalues for input fields in the page description for each printednetpage.

The relationship between the page description, the page instance, andthe printed netpage is shown in FIG. 4. The printed netpage may be partof a printed netpage document 45. The page instance is associated withboth the netpage printer which printed it and, if known, the netpageuser who requested it.

1.2 Netpage Tags

1.2.1 Tag Data Content

In a preferred form, each tag identifies the region in which it appears,and the location of that tag within the region. A tag may also containflags which relate to the region as a whole or to the tag. One or moreflag bits may, for example, signal a tag sensing device to providefeedback indicative of a function associated with the immediate area ofthe tag, without the sensing device having to refer to a description ofthe region. A netpage pen may, for example, illuminate an “active area”LED when in the zone of a hyperlink.

As will be more clearly explained below, in a preferred embodiment, eachtag contains an easily recognized invariant structure which aids initialdetection, and which assists in minimizing the effect of any warpinduced by the surface or by the sensing process. The tags preferablytile the entire page, and are sufficiently small and densely arrangedthat the pen can reliably image at least one tag even on a single clickon the page. It is important that the pen recognize the page ID andposition on every interaction with the page, since the interaction isstateless.

In a preferred embodiment, the region to which a tag refers coincideswith an entire page, and the region ID encoded in the tag is thereforesynonymous with the page ID of the page on which the tag appears. Inother embodiments, the region to which a tag refers can be an arbitrarysubregion of a page or other surface. For example, it can coincide withthe zone of an interactive element, in which case the region ID candirectly identify the interactive element.

TABLE 1 Tag data Field Precision (bits) Region ID 100 Tag ID  16 Flags 4 Total 120

Each tag contains 120 bits of information, typically allocated as shownin Table 1. Assuming a maximum tag density of 64 per square inch, a16-bit tag ID supports a region size of up to 1024 square inches. Largerregions can be mapped continuously without increasing the tag IDprecision simply by using abutting regions and maps. The 100-bit regionID allows 2¹⁰⁰ (˜10³⁰ or a million trillion trillion) different regionsto be uniquely identified.

1.2.2 Tag Data Encoding

The 120 bits of tag data are redundantly encoded using a (15, 5)Reed-Solomon code. This yields 360 encoded bits consisting of 6codewords of 15 4-bit symbols each. The (15, 5) code allows up to 5symbol errors to be corrected per codeword, i.e. it is tolerant of asymbol error rate of up to 33% per codeword.

Each 4-bit symbol is represented in a spatially coherent way in the tag,and the symbols of the six codewords are interleaved spatially withinthe tag. This ensures that a burst error (an error affecting multiplespatially adjacent bits) damages a minimum number of symbols overall anda minimum number of symbols in any one codeword, thus maximising thelikelihood that the burst error can be fully corrected.

Any suitable error-correcting code code can be used in place of a (15,5) Reed-Solomon code, for example a Reed-Solomon code with more or lessredundancy, with the same or different symbol and codeword sizes;another block code; or a different kind of code, such as a convolutionalcode (see, for example, Stephen B. Wicker, Error Control Systems forDigital Communication and Storage, Prentice-Hall 1995, the contents ofwhich a herein incorporated by cross-reference).

1.2.3 Physical Tag Structure

The physical representation of the tag, shown in FIG. 5 a, includesfixed target structures 15, 16, 17 and variable data areas 18. The fixedtarget structures allow a sensing device such as the netpage pen todetect the tag and infer its three-dimensional orientation relative tothe sensor. The data areas contain representations of the individualbits of the encoded tag data.

To achieve proper tag reproduction, the tag is rendered at a resolutionof 256×256 dots. When printed at 1600 dots per inch this yields a tagwith a diameter of about 4 mm. At this resolution the tag is designed tobe surrounded by a “quiet area” of radius 16 dots. Since the quiet areais also contributed by adjacent tags, it only adds 16 dots to theeffective diameter of the tag.

The tag includes six target structures. A detection ring 15 allows thesensing device to initially detect the tag. The ring is easy to detectbecause it is rotationally invariant and because a simple correction ofits aspect ratio removes most of the effects of perspective distortion.An orientation axis 16 allows the sensing device to determine theapproximate planar orientation of the tag due to the yaw of the sensor.The orientation axis is skewed to yield a unique orientation. Fourperspective targets 17 allow the sensing device to infer an accuratetwo-dimensional perspective transform of the tag and hence an accuratethree-dimensional position and orientation of the tag relative to thesensor.

All target structures are redundantly large to improve their immunity tonoise.

The overall tag shape is circular. This supports, amongst other things,optimal tag packing on an irregular triangular grid. In combination withthe circular detection ring, this makes a circular arrangement of databits within the tag optimal. To maximise its size, each data bit isrepresented by a radial wedge in the form of an area bounded by tworadial lines and two concentric circular arcs. Each wedge has a minimumdimension of 8 dots at 1600 dpi and is designed so that its base (itsinner arc), is at least equal to this minimum dimension. The height ofthe wedge in the radial direction is always equal to the minimumdimension. Each 4-bit data symbol is represented by an array of 2×2wedges.

The 15 4-bit data symbols of each of the six codewords are allocated tothe four concentric symbol rings 18 a to 18 d in interleaved fashion.Symbols are allocated alternately in circular progression around thetag.

The interleaving is designed to maximise the average spatial distancebetween any two symbols of the same codeword.

In order to support “single-click” interaction with a tagged region viaa sensing device, the sensing device must be able to see at least oneentire tag in its field of view no matter where in the region or at whatorientation it is positioned. The required diameter of the field of viewof the sensing device is therefore a function of the size and spacing ofthe tags.

Assuming a circular tag shape, the minimum diameter of the sensor fieldof view is obtained when the tags are tiled on a equilateral triangulargrid, as shown in FIG. 5 b.

1.2.4 Tag Image Processing and Decoding

The tag image processing and decoding performed by a sensing device suchas the netpage pen is shown in FIG. 7. While a captured image is beingacquired from the image sensor, the dynamic range of the image isdetermined (at 20). The center of the range is then chosen as the binarythreshold for the image 21. The image is then thresholded and segmentedinto connected pixel regions (i.e. shapes 23) (at 22). Shapes which aretoo small to represent tag target structures are discarded. The size andcentroid of each shape is also computed.

Binary shape moments 25 are then computed (at 24) for each shape, andthese provide the basis for subsequently locating target structures.Central shape moments are by their nature invariant of position, and canbe easily made invariant of scale, aspect ratio and rotation.

The ring target structure 15 is the first to be located (at 26). A ringhas the advantage of being very well behaved when perspective-distorted.Matching proceeds by aspect-normalizing and rotation-normalizing eachshape's moments. Once its second-order moments are normalized the ringis easy to recognize even if the perspective distortion was significant.The ring's original aspect and rotation 27 together provide a usefulapproximation of the perspective transform.

The axis target structure 16 is the next to be located (at 28). Matchingproceeds by applying the ring's normalizations to each shape's moments,and rotation-normalizing the resulting moments. Once its second-ordermoments are normalized the axis target is easily recognized. Note thatone third order moment is required to disambiguate the two possibleorientations of the axis. The shape is deliberately skewed to one sideto make this possible Note also that it is only possible torotation-normalize the axis target after it has had the ring'snormalizations applied, since the perspective distortion can hide theaxis target's axis. The axis target's original rotation provides auseful approximation of the tag's rotation due to pen yaw 29.

The four perspective target structures 17 are the last to be located (at30). Good estimates of their positions are computed based on their knownspatial relationships to the ring and axis targets, the aspect androtation of the ring, and the rotation of the axis. Matching proceeds byapplying the ring's normalizations to each shape's moments. Once theirsecond-order moments are normalized the circular perspective targets areeasy to recognize, and the target closest to each estimated position istaken as a match. The original centroids of the four perspective targetsare then taken to be the perspective-distorted corners 31 of a square ofknown size in tag space, and an eight-degree-of-freedom perspectivetransform 33 is inferred (at 32) based on solving the well-understoodequations relating the four tag-space and image-space point pairs (seeHeckbert, P., Fundamentals of Texture Mapping and Image Warping, MastersThesis, Dept. of EECS, U. of California at Berkeley, Technical ReportNo. UCB/CSD 89/516, June 1989, the contents of which are hereinincorporated by cross-reference).

The inferred tag-space to image-space perspective transform is used toproject (at 36) each known data bit position in tag space into imagespace where the real-valued position is used to bilinearly interpolate(at 36) the four relevant adjacent pixels in the input image. Thepreviously computed image threshold 21 is used to threshold the resultto produce the final bit value 37.

Once all 360 data bits 37 have been obtained in this way, each of thesix 60-bit Reed-Solomon codewords is decoded (at 38) to yield 20 decodedbits 39, or 120 decoded bits in total. Note that the codeword symbolsare sampled in codeword order, so that codewords are implicitlyde-interleaved during the sampling process.

The ring target 15 is only sought in a subarea of the image whoserelationship to the image guarantees that the ring, if found, is part ofa complete tag. If a complete tag is not found and successfully decoded,then no pen position is recorded for the current frame. Given adequateprocessing power and ideally a non-minimal field of view 193, analternative strategy involves seeking another tag in the current image.

The obtained tag data indicates the identity of the region containingthe tag and the position of the tag within the region. An accurateposition 35 of the pen nib in the region, as well as the overallorientation 35 of the pen, is then inferred (at 34) from the perspectivetransform 33 observed on the tag and the known spatial relationshipbetween the pen's physical axis and the pen's optical axis.

1.2.5 Alternative Tag Structures

The tag structure described above is designed to support the tagging ofnon-planar surfaces where a regular tiling of tags may not be possible.In the more usual case of planar surfaces where a regular tiling of tagsis possible, i.e. surfaces such as sheets of paper and the like, moreefficient tag structures can be used which exploit the regular nature ofthe tiling.

FIG. 6 a shows a square tag 4 with four perspective targets 17. It issimilar in structure to tags described by Bennett et al. in U.S. Pat.No. 5,051,746. The tag represents sixty 4-bit Reed-Solomon symbols 47,for a total of 240 bits. The tag represents each one bit as a dot 48,and each zero bit by the absence of the corresponding dot. Theperspective targets are designed to be shared between adjacent tags, asshown in FIGS. 6 b and 6 c. FIG. 6 b shows a square tiling of 16 tagsand the corresponding minimum field of view 193, which must span thediagonals of two tags. FIG. 6 c shows a square tiling of nine tags,containing all one bits for illustration purposes.

Using a (15, 7) Reed-Solomon code, 112 bits of tag data are redundantlyencoded to produce 240 encoded bits. The four codewords are interleavedspatially within the tag to maximize resilience to burst errors.Assuming a 16-bit tag ID as before, this allows a region ID of up to 92bits.

The data-bearing dots 48 of the tag are designed to not overlap theirneighbors, so that groups of tags cannot produce structures whichresemble targets. This also saves ink. The perspective targets thereforeallow detection of the tag, so further targets are not required. Tagimage processing proceeds as described in section 1.2.4 above, with theexception that steps 26 and 28 are omitted.

Although the tag may contain an orientation feature to allowdisambiguation of the four possible orientations of the tag relative tothe sensor, it is also possible to embed orientation data in the tagdata. For example, the four codewords can be arranged so that each tagorientation contains one codeword placed at that orientation, as shownin FIG. 6 d, where each symbol is labelled with the number of itscodeword (1-4) and the position of the symbol within the codeword (A-O).Tag decoding then consists of decoding one codeword at each orientation.Each codeword can either contain a single bit indicating whether it isthe first codeword, or two bits indicating which codeword it is. Thelatter approach has the advantage that if, say, the data content of onlyone codeword is required, then at most two codewords need to be decodedto obtain the desired data. This may be the case if the region ID is notexpected to change within a stroke and is thus only decoded at the startof a stroke. Within a stroke only the codeword containing the tag ID isthen desired. Furthermore, since the rotation of the sensing devicechanges slowly and predictably within a stroke, only one codewordtypically needs to be decoded per frame.

It is possible to dispense with perspective targets altogether andinstead rely on the data representation being self-registering. In thiscase each bit value (or multi-bit value) is typically represented by anexplicit glyph, i.e. no bit value is represented by the absence of aglyph. This ensures that the data grid is well-populated, and thusallows the grid to be reliably identified and its perspective distortiondetected and subsequently corrected during data sampling. To allow tagboundaries to be detected, each tag data must contain a marker pattern,and these must be redundantly encoded to allow reliable detection. Theoverhead of such marker patterns is similar to the overhead of explicitperspective targets. One such scheme uses dots positioned a variouspoints relative to grid vertices to represent different glyphs and hencedifferent multi-bit values (see Anoto Technology Description, AnotoApril 2000).

1.2.6 Tag Map

Decoding a tag results in a region ID, a tag ID, and a tag-relative pentransform. Before the tag ID and the tag-relative pen location can betranslated into an absolute location within the tagged region, thelocation of the tag within the region must be known. This is given by atag map, a function which maps each tag ID in a tagged region to acorresponding location. The tag map class diagram is shown in FIG. 22,as part of the netpage printer class diagram.

A tag map reflects the scheme used to tile the surface region with tags,and this can vary according to surface type. When multiple taggedregions share the same tiling scheme and the same tag numbering scheme,they can also share the same tag map.

The tag map for a region must be retrievable via the region ID. Thus,given a region ID, a tag ID and a pen transform, the tag map can beretrieved, the tag ID can be translated into an absolute tag locationwithin the region, and the tag-relative pen location can be added to thetag location to yield an absolute pen location within the region.

The tag ID may have a structure which assists translation through thetag map. It may, for example, encoded Cartesian coordinates or polarcoordinates, depending on the surface type on which it appears. The tagID structure is dictated by and known to the tag map, and tag IDsassociated with different tag maps may therefore have differentstructures.

1.2.7 Tagging Schemes

Two distinct surface coding schemes are of interest, both of which usethe tag structure described earlier in this section. The preferredcoding scheme uses “location-indicating” tags as already discussed. Analternative coding scheme uses object-indicating tags.

A location-indicating tag contains a tag ID which, when translatedthrough the tag map associated with the tagged region, yields a uniquetag location within the region. The tag-relative location of the pen isadded to this tag location to yield the location of the pen within theregion. This in turn is used to determine the location of the penrelative to a user interface element in the page description associatedwith the region. Not only is the user interface element itselfidentified, but a location relative to the user interface element isidentified. Location-indicating tags therefore trivially support thecapture of an absolute pen path in the zone of a particular userinterface element.

An object-indicating tag contains a tag ID which directly identifies auser interface element in the page description associated with theregion. All the tags in the zone of the user interface element identifythe user interface element, making them all identical and thereforeindistinguishable. Object-indicating tags do not, therefore, support thecapture of an absolute pen path. They do, however, support the captureof a relative pen path. So long as the position sampling frequencyexceeds twice the encountered tag frequency, the displacement from onesampled pen position to the next within a stroke can be unambiguouslydetermined.

With either tagging scheme, the tags function in cooperation withassociated visual elements on the netpage as user interactive elementsin that a user can interact with the printed page using an appropriatesensing device in order for tag data to be read by the sensing deviceand for an appropriate response to be generated in the netpage system.

1.3 Document and Page Descriptions

A preferred embodiment of a document and page description class diagramis shown in FIGS. 25 and 26.

In the netpage system a document is described at three levels. At themost abstract level the document 836 has a hierarchical structure whoseterminal elements 839 are associated with content objects 840 such astext objects, text style objects, image objects, etc. Once the documentis printed on a printer with a particular page size and according to aparticular user's scale factor preference, the document is paginated andotherwise formatted. Formatted terminal elements 835 will in some casesbe associated with content objects which are different from thoseassociated with their corresponding terminal elements, particularlywhere the content objects are style-related. Each printed instance of adocument and page is also described separately, to allow input capturedthrough a particular page instance 830 to be recorded separately frominput captured through other instances of the same page description.

The presence of the most abstract document description on the pageserver allows a user to request a copy of a document without beingforced to accept the source document's specific format. The user may berequesting a copy through a printer with a different page size, forexample. Conversely, the presence of the formatted document descriptionon the page server allows the page server to efficiently interpret useractions on a particular printed page.

A formatted document 834 consists of a set of formatted pagedescriptions 5, each of which consists of a set of formatted terminalelements 835. Each formatted element has a spatial extent or zone 58 onthe page. This defines the active area of input elements such ashyperlinks and input fields.

A document instance 831 corresponds to a formatted document 834. Itconsists of a set of page instances 830, each of which corresponds to apage description 5 of the formatted document. Each page instance 830describes a single unique printed netpage 1, and records the page ID 50of the netpage. A page instance is not part of a document instance if itrepresents a copy of a page requested in isolation.

A page instance consists of a set of terminal element instances 832. Anelement instance only exists if it records instance-specificinformation. Thus, a hyperlink instance exists for a hyperlink elementbecause it records a transaction ID 55 which is specific to the pageinstance, and a field instance exists for a field element because itrecords input specific to the page instance. An element instance doesnot exist, however, for static elements such as textflows.

A terminal element can be a static element 843, a hyperlink element 844,a field element 845 or a page server command element 846, as shown inFIG. 27. A static element 843 can be a style element 847 with anassociated style object 854, a textflow element 848 with an associatedstyled text object 855, an image element 849 with an associated imageelement 856, a graphic element 850 with an associated graphic object857, a video clip element 851 with an associated video clip object 858,an audio clip element 852 with an associated audio clip object 859, or ascript element 853 with an associated script object 860, as shown inFIG. 28.

A page instance has a background field 833 which is used to record anydigital ink captured on the page which does not apply to a specificinput element.

In the preferred form of the invention, a tag map 811 is associated witheach page instance to allow tags on the page to be translated intolocations on the page.

1.4 The Netpage Network

In a preferred embodiment, a netpage network consists of a distributedset of netpage page servers 10, netpage registration servers 11, netpageID servers 12, netpage application servers 13, netpage publicationservers 14, and netpage printers 601 connected via a network 19 such asthe Internet, as shown in FIG. 3.

The netpage registration server 11 is a server which recordsrelationships between users, pens, printers, applications andpublications, and thereby authorizes various network activities. Itauthenticates users and acts as a signing proxy on behalf ofauthenticated users in application transactions. It also provideshandwriting recognition services. As described above, a netpage pageserver 10 maintains persistent information about page descriptions andpage instances. The netpage network includes any number of page servers,each handling a subset of page instances. Since a page server alsomaintains user input values for each page instance, clients such asnetpage printers send netpage input directly to the appropriate pageserver. The page server interprets any such input relative to thedescription of the corresponding page.

A netpage ID server 12 allocates document IDs 51 on demand, and providesload-balancing of page servers via its ID allocation scheme.

A netpage printer uses the Internet Distributed Name System (DNS), orsimilar, to resolve a netpage page ID 50 into the network address of thenetpage page server handling the corresponding page instance.

A netpage application server 13 is a server which hosts interactivenetpage applications. A netpage publication server 14 is an applicationserver which publishes netpage documents to netpage printers. They aredescribed in detail in Section 2.

Netpage servers can be hosted on a variety of network server platformsfrom manufacturers such as IBM, Hewlett-Packard, and Sun. Multiplenetpage servers can run concurrently on a single host, and a singleserver can be distributed over a number of hosts. Some or all of thefunctionality provided by netpage servers, and in particular thefunctionality provided by the ID server and the page server, can also beprovided directly in a netpage appliance such as a netpage printer, in acomputer workstation, or on a local network.

1.5 The Netpage Printer

The netpage printer 601 is an appliance which is registered with thenetpage system and prints netpage documents on demand and viasubscription. Each printer has a unique printer ID 62, and is connectedto the netpage network via a network such as the Internet, ideally via abroadband connection.

Apart from identity and security settings in non-volatile memory, thenetpage printer contains no persistent storage. As far as a user isconcerned, “the network is the computer”. Netpages functioninteractively across space and time with the help of the distributednetpage page servers 10, independently of particular netpage printers.

The netpage printer receives subscribed netpage documents from netpagepublication servers 14. Each document is distributed in two parts: thepage layouts, and the actual text and image objects which populate thepages. Because of personalization, page layouts are typically specificto a particular subscriber and so are pointcast to the subscriber'sprinter via the appropriate page server. Text and image objects, on theother hand, are typically shared with other subscribers, and so aremulticast to all subscribers' printers and the appropriate page servers.

The netpage publication server optimizes the segmentation of documentcontent into pointcasts and multicasts. After receiving the pointcast ofa document's page layouts, the printer knows which multicasts, if any,to listen to.

Once the printer has received the complete page layouts and objects thatdefine the document to be printed, it can print the document.

The printer rasterizes and prints odd and even pages simultaneously onboth sides of the sheet. It contains duplexed print engine controllers760 and print engines utilizing Memjet™ printheads 350 for this purpose.

The printing process consists of two decoupled stages: rasterization ofpage descriptions, and expansion and printing of page images. The rasterimage processor (RIP) consists of one or more standard DSPs 757 runningin parallel. The duplexed print engine controllers consist of customprocessors which expand, dither and print page images in real time,synchronized with the operation of the printheads in the print engines.

Printers not enabled for IR printing have the option to print tags usingIR-absorptive black ink, although this restricts tags to otherwise emptyareas of the page. Although such pages have more limited functionalitythan IR-printed pages, they are still classed as netpages.

A normal netpage printer prints netpages on sheets of paper. Morespecialised netpage printers may print onto more specialised surfaces,such as globes. Each printer supports at least one surface type, andsupports at least one tag tiling scheme, and hence tag map, for eachsurface type. The tag map 811 which describes the tag tiling schemeactually used to print a document becomes associated with that documentso that the document's tags can be correctly interpreted.

FIG. 2 shows the netpage printer class diagram, reflectingprinter-related information maintained by a registration server 11 onthe netpage network.

A preferred embodiment of the netpage printer is described in greaterdetail in Section 6 below, with reference to FIGS. 11 to 16.

1.5.1 Memjet™ Printheads

The netpage system can operate using printers made with a wide range ofdigital printing technologies, including thermal inkjet, piezoelectricinkjet, laser electrophotographic, and others. However, for wideconsumer acceptance, it is desirable that a netpage printer have thefollowing characteristics:

-   -   photographic quality color printing    -   high quality text printing    -   high reliability    -   low printer cost    -   low ink cost    -   low paper cost    -   simple operation    -   nearly silent printing    -   high printing speed    -   simultaneous double sided printing    -   compact form factor    -   low power consumption

No commercially available printing technology has all of thesecharacteristics.

To enable to production of printers with these characteristics, thepresent applicant has invented a new print technology, referred to asMemjet™ technology. Memjet™ is a drop-on-demand inkjet technology thatincorporates pagewidth printheads fabricated usingmicroelectromechanical systems (MEMS) technology. FIG. 17 shows a singleprinting element 300 of a Memjet™ printhead. The netpage wallprinterincorporates 168960 printing elements 300 to form a 1600 dpi pagewidthduplex printer. This printer simultaneously prints cyan, magenta,yellow, black, and infrared inks as well as paper conditioner and inkfixative.

The printing element 300 is approximately 110 microns long by 32 micronswide. Arrays of these printing elements are formed on a siliconsubstrate 301 that incorporates CMOS logic, data transfer, timing, anddrive circuits (not shown).

Major elements of the printing element 300 are the nozzle 302, thenozzle rim 303, the nozzle chamber 304, the fluidic seal 305, the inkchannel rim 306, the lever arm 307, the active actuator beam pair 308,the passive actuator beam pair 309, the active actuator anchor 310, thepassive actuator anchor 311, and the ink inlet 312.

The active actuator beam pair 308 is mechanically joined to the passiveactuator beam pair 309 at the join 319. Both beams pairs are anchored attheir respective anchor points 310 and 311. The combination of elements308, 309, 310, 311, and 319 form a cantilevered electrothermal bendactuator 320.

FIG. 18 shows a small part of an array of printing elements 300,including a cross section 315 of a printing element 300. The crosssection 315 is shown without ink, to clearly show the ink inlet 312 thatpasses through the silicon wafer 301.

FIGS. 19(a), 19(b) and 19(c) show the operating cycle of a Memjet™printing element 300.

FIG. 19(a) shows the quiescent position of the ink meniscus 316 prior toprinting an ink droplet. Ink is retained in the nozzle chamber bysurface tension at the ink meniscus 316 and at the fluidic seal 305formed between the nozzle chamber 304 and the ink channel rim 306.

While printing, the printhead CMOS circuitry distributes data from theprint engine controller to the correct printing element, latches thedata, and buffers the data to drive the electrodes 318 of the activeactuator beam pair 308. This causes an electrical current to passthrough the beam pair 308 for about one microsecond, resulting in Jouleheating. The temperature increase resulting from Joule heating causesthe beam pair 308 to expand. As the passive actuator beam pair 309 isnot heated, it does not expand, resulting in a stress difference betweenthe two beam pairs. This stress difference is partially resolved by thecantilevered end of the electrothermal bend actuator 320 bending towardsthe substrate 301. The lever arm 307 transmits this movement to thenozzle chamber 304. The nozzle chamber 304 moves about two microns tothe position shown in FIG. 19(b). This increases the ink pressure,forcing ink 321 out of the nozzle 302, and causing the ink meniscus 316to bulge. The nozzle rim 303 prevents the ink meniscus 316 fromspreading across the surface of the nozzle chamber 304.

As the temperature of the beam pairs 308 and 309 equalizes, the actuator320 returns to its original position. This aids in the break-off of theink droplet 317 from the ink 321 in the nozzle chamber, as shown in FIG.19(c). The nozzle chamber is refilled by the action of the surfacetension at the meniscus 316.

FIG. 20 shows a segment of a printhead 350. In a netpage printer, thelength of the printhead is the full width of the paper (typically 210mm) in the direction 351. The segment shown is 0.4 mm long (about 0.2%of a complete printhead). When printing, the paper is moved past thefixed printhead in the direction 352. The printhead has 6 rows ofinterdigitated printing elements 300, printing the six colors or typesof ink supplied by the ink inlets 312.

To protect the fragile surface of the printhead during operation, anozzle guard wafer 330 is attached to the printhead substrate 301. Foreach nozzle 302 there is a corresponding nozzle guard hole 331 throughwhich the ink droplets are fired. To prevent the nozzle guard holes 331from becoming blocked by paper fibers or other debris, filtered air ispumped through the air inlets 332 and out of the nozzle guard holesduring printing. To prevent ink 321 from drying, the nozzle guard issealed while the printer is idle.

1.6 The Netpage Pen

The active sensing device of the netpage system is typically a pen 101,which, using its embedded controller 134, is able to capture and decodeIR position tags from a page via an image sensor. The image sensor is asolid-state device provided with an appropriate filter to permit sensingat only near-infrared wavelengths. As described in more detail below,the system is able to sense when the nib is in contact with the surface,and the pen is able to sense tags at a sufficient rate to capture humanhandwriting (i.e. at 200 dpi or greater and 100 Hz or faster).Information captured by the pen is encrypted and wirelessly transmittedto the printer (or base station), the printer or base stationinterpreting the data with respect to the (known) page structure.

The preferred embodiment of the netpage pen operates both as a normalmarking ink pen and as a non-marking stylus. The marking aspect,however, is not necessary for using the netpage system as a browsingsystem, such as when it is used as an Internet interface. Each netpagepen is registered with the netpage system and has a unique pen ID 61.FIG. 23, shows the netpage pen class diagram, reflecting pen-relatedinformation maintained by a registration server 11 on the netpagenetwork.

When either nib is in contact with a netpage, the pen determines itsposition and orientation relative to the page. The nib is attached to aforce sensor, and the force on the nib is interpreted relative to athreshold to indicate whether the pen is “up” or “down”. This allows ainteractive element on the page to be ‘clicked’ by pressing with the pennib, in order to request, say, information from a network. Furthermore,the force is captured as a continuous value to allow, say, the fulldynamics of a signature to be verified.

The pen determines the position and orientation of its nib on thenetpage by imaging, in the infrared spectrum, an area 193 of the page inthe vicinity of the nib. It decodes the nearest tag and computes theposition of the nib relative to the tag from the observed perspectivedistortion on the imaged tag and the known geometry of the pen optics.Although the position resolution of the tag may be low, because the tagdensity on the page is inversely proportional to the tag size, theadjusted position resolution is quite high, exceeding the minimumresolution required for accurate handwriting recognition.

Pen actions relative to a netpage are captured as a series of strokes. Astroke consists of a sequence of time-stamped pen positions on the page,initiated by a pen-down event and completed by the subsequent pen-upevent. A stroke is also tagged with the page ID 50 of the netpagewhenever the page ID changes, which, under normal circumstances, is atthe commencement of the stroke.

Each netpage pen has a current selection 826 associated with it,allowing the user to perform copy and paste operations etc. Theselection is timestamped to allow the system to discard it after adefined time period. The current selection describes a region of a pageinstance. It consists of the most recent digital ink stroke capturedthrough the pen relative to the background area of the page. It isinterpreted in an application-specific manner once it is submitted to anapplication via a selection hyperlink activation.

Each pen has a current nib 824. This is the nib last notified by the pento the system. In the case of the default netpage pen described above,either the marking black ink nib or the non-marking stylus nib iscurrent. Each pen also has a current nib style 825. This is the nibstyle last associated with the pen by an application, e.g. in responseto the user selecting a color from a palette. The default nib style isthe nib style associated with the current nib. Strokes captured througha pen are tagged with the current nib style. When the strokes aresubsequently reproduced, they are reproduced in the nib style with whichthey are tagged.

Whenever the pen is within range of a printer with which it cancommunicate, the pen slowly flashes its “online” LED. When the pen failsto decode a stroke relative to the page, it momentarily activates its“error” LED. When the pen succeeds in decoding a stroke relative to thepage, it momentarily activates its “ok” LED.

A sequence of captured strokes is referred to as digital ink. Digitalink forms the basis for the digital exchange of drawings andhandwriting, for online recognition of handwriting, and for onlineverification of signatures.

The pen is wireless and transmits digital ink to the netpage printer viaa short-range radio link. The transmitted digital ink is encrypted forprivacy and security and packetized for efficient transmission, but isalways flushed on a pen-up event to ensure timely handling in theprinter.

When the pen is out-of-range of a printer it buffers digital ink ininternal memory, which has a capacity of over ten minutes of continuoushandwriting. When the pen is once again within range of a printer, ittransfers any buffered digital ink.

A pen can be registered with any number of printers, but because allstate data resides in netpages both on paper and on the network, it islargely immaterial which printer a pen is communicating with at anyparticular time.

A preferred embodiment of the pen is described in greater detail inSection 6 below, with reference to FIGS. 8 to 10.

1.7 Netpage Interaction

The netpage printer 601 receives data relating to a stroke from the pen101 when the pen is used to interact with a netpage 1. The coded data 3of the tags 4 is read by the pen when it is used to execute a movement,such as a stroke. The data allows the identity of the particular pageand associated interactive element to be determined and an indication ofthe relative positioning of the pen relative to the page to be obtained.The indicating data is transmitted to the printer, where it resolves,via the DNS, the page ID 50 of the stroke into the network address ofthe netpage page server 10 which maintains the corresponding pageinstance 830. It then transmits the stroke to the page server. If thepage was recently identified in an earlier stroke, then the printer mayalready have the address of the relevant page server in its cache. Eachnetpage consists of a compact page layout maintained persistently by anetpage page server (see below). The page layout refers to objects suchas images, fonts and pieces of text, typically stored elsewhere on thenetpage network.

When the page server receives the stroke from the pen, it retrieves thepage description to which the stroke applies, and determines whichelement of the page description the stroke intersects. It is then ableto interpret the stroke in the context of the type of the relevantelement.

A “click” is a stroke where the distance and time between the pen downposition and the subsequent pen up position are both less than somesmall maximum. An object which is activated by a click typicallyrequires a click to be activated, and accordingly, a longer stroke isignored. The failure of a pen action, such as a “sloppy” click, toregister is indicated by the lack of response from the pen's “ok” LED.

There are two kinds of input elements in a netpage page description:hyperlinks and form fields. Input through a form field can also triggerthe activation of an associated hyperlink.

1.7.1 Hyperlinks

A hyperlink is a means of sending a message to a remote application, andtypically elicits a printed response in the netpage system.

A hyperlink element 844 identifies the application 71 which handlesactivation of the hyperlink, a link ID 54 which identifies the hyperlinkto the application, an “alias required” flag which asks the system toinclude the user's application alias ID 65 in the hyperlink activation,and a description which is used when the hyperlink is recorded as afavorite or appears in the user's history. The hyperlink element classdiagram is shown in FIG. 29.

When a hyperlink is activated, the page server sends a request to anapplication somewhere on the network. The application is identified byan application ID 64, and the application ID is resolved in the normalway via the DNS. There are three types of hyperlinks: general hyperlinks863, form hyperlinks 865, and selection hyperlinks 864, as shown in FIG.30. A general hyperlink can implement a request for a linked document,or may simply signal a preference to a server. A form hyperlink submitsthe corresponding form to the application. A selection hyperlink submitsthe current selection to the application. If the current selectioncontains a single-word piece of text, for example, the application mayreturn a single-page document giving the word's meaning within thecontext in which it appears, or a translation into a different language.Each hyperlink type is characterized by what information is submitted tothe application.

The corresponding hyperlink instance 862 records a transaction ID 55which can be specific to the page instance on which the hyperlinkinstance appears. The transaction ID can identify user-specific data tothe application, for example a “shopping cart” of pending purchasesmaintained by a purchasing application on behalf of the user.

The system includes the pen's current selection 826 in a selectionhyperlink activation. The system includes the content of the associatedform instance 868 in a form hyperlink activation, although if thehyperlink has its “submit delta” attribute set, only input since thelast form submission is included. The system includes an effectivereturn path in all hyperlink activations.

A hyperlinked group 866 is a group element 838 which has an associatedhyperlink, as shown in FIG. 31. When input occurs through any fieldelement in the group, the hyperlink 844 associated with the group isactivated. A hyperlinked group can be used to associate hyperlinkbehavior with a field such as a checkbox. It can also be used, inconjunction with the “submit delta” attribute of a form hyperlink, toprovide continuous input to an application. It can therefore be used tosupport a “blackboard” interaction model, i.e. where input is capturedand therefore shared as soon as it occurs.

1.7.2 Forms

A form defines a collection of related input fields used to capture arelated set of inputs through a printed netpage. A form allows a user tosubmit one or more parameters to an application software program runningon a server.

A form 867 is a group element 838 in the document hierarchy. Itultimately contains a set of terminal field elements 839. A forminstance 868 represents a printed instance of a form. It consists of aset of field instances 870 which correspond to the field elements 845 ofthe form. Each field instance has an associated value 871, whose typedepends on the type of the corresponding field element. Each field valuerecords input through a particular printed form instance, i.e. throughone or more printed netpages. The form class diagram is shown in FIG.32.

Each form instance has a status 872 which indicates whether the form isactive, frozen, submitted, void or expired. A form is active when firstprinted. A form becomes frozen once it is signed or once its freeze timeis reached. A form becomes submitted once one of its submissionhyperlinks has been activated, unless the hyperlink has its “submitdelta” attribute set. A form becomes void when the user invokes a voidform, reset form or duplicate form page command. A form expires when itsspecified expiry time is reached, i.e. when the time the form has beenactive exceeds the form's specified lifetime. While the form is active,form input is allowed. Input through a form which is not active isinstead captured in the background field 833 of the relevant pageinstance. When the form is active or frozen, form submission is allowed.Any attempt to submit a form when the form is not active or frozen isrejected, and instead elicits an form status report.

Each form instance is associated (at 59) with any form instances derivedfrom it, thus providing a version history. This allows all but thelatest version of a form in a particular time period to be excluded froma search.

All input is captured as digital ink. Digital ink 873 consists of a setof timestamped stroke groups 874, each of which consists of a set ofstyled strokes 875. Each stroke consists of a set of timestamped penpositions 876, each of which also includes pen orientation and nibforce. The digital ink class diagram is shown in FIG. 33.

A field element 845 can be a checkbox field 877, a text field 878, adrawing field 879, or a signature field 880. The field element classdiagram is shown in FIG. 34. Any digital ink captured in a field's zone58 is assigned to the field.

A checkbox field has an associated boolean value 881, as shown in FIG.35. Any mark (a tick, a cross, a stroke, a fill zigzag, etc.) capturedin a checkbox field's zone causes a true value to be assigned to thefield's value.

A text field has an associated text value 882, as shown in FIG. 36. Anydigital ink captured in a text field's zone is automatically convertedto text via online handwriting recognition, and the text is assigned tothe field's value. Online handwriting recognition is well-understood(see, for example, Tappert, C., C. Y. Suen and T. Wakahara, “The Stateof the Art in On-Line Handwriting Recognition”, IEEE Transactions onPattern Analysis and Machine Intelligence, Vol. 12, No. 8, August 1990,the contents of which are herein incorporated by cross-reference).

A signature field has an associated digital signature value 883, asshown in FIG. 37. Any digital ink captured in a signature field's zoneis automatically verified with respect to the identity of the owner ofthe pen, and a digital signature of the content of the form of which thefield is part is generated and assigned to the field's value. Thedigital signature is generated using the pen user's private signaturekey specific to the application which owns the form. Online signatureverification is well-understood (see, for example, Plamondon, R. and G.Lorette, “Automatic Signature Verification and Writer Identification—TheState of the Art”, Pattern Recognition, Vol. 22, No. 2, 1989, thecontents of which are herein incorporated by cross-reference).

A field element is hidden if its “hidden” attribute is set. A hiddenfield element does not have an input zone on a page and does not acceptinput. It can have an associated field value which is included in theform data when the form containing the field is submitted.

“Editing” commands, such as strike-throughs indicating deletion, canalso be recognized in form fields.

Because the handwriting recognition algorithm works “online” (i.e. withaccess to the dynamics of the pen movement), rather than “offline” (i.e.with access only to a bitmap of pen markings), it can recognize run-ondiscretely-written characters with relatively high accuracy, without awriter-dependent training phase. A writer-dependent model of handwritingis automatically generated over time, however, and can be generatedup-front if necessary,

Digital ink, as already stated, consists of a sequence of strokes. Anystroke which starts in a particular element's zone is appended to thatelement's digital ink stream, ready for interpretation. Any stroke notappended to an object's digital ink stream is appended to the backgroundfield's digital ink stream.

Digital ink captured in the background field is interpreted as aselection gesture. Circumscription of one or more objects is generallyinterpreted as a selection of the circumscribed objects, although theactual interpretation is application-specific.

Table 2 summarises these various pen interactions with a netpage.

TABLE 2 Summary of pen interactions with a netpage Object Type Pen inputAction Hyperlink General Click Submit action to application Form ClickSubmit form to application Selection Click Submit selection to appli-cation Form field Checkbox Any mark Assign true to field TextHandwriting Convert digital ink to text; assign text to field DrawingDigital ink Assign digital ink to field Signature Signature Verifydigital ink signature; generate digital signature of form; assigndigital signature to field None — Circumscription Assign digital ink tocurrent selection

The system maintains a current selection for each pen. The selectionconsists simply of the most recent stroke captured in the backgroundfield. The selection is cleared after an inactivity timeout to ensurepredictable behavior.

The raw digital ink captured in every field is retained on the netpagepage server and is optionally transmitted with the form data when theform is submitted to the application. This allows the application tointerrogate the raw digital ink should it suspect the originalconversion, such as the conversion of handwritten text. This can, forexample, involve human intervention at the application level for formswhich fail certain application-specific consistency checks. As anextension to this, the entire background area of a form can bedesignated as a drawing field. The application can then decide, on thebasis of the presence of digital ink outside the explicit fields of theform, to route the form to a human operator, on the assumption that theuser may have indicated amendments to the filled-in fields outside ofthose fields.

FIG. 38 shows a flowchart of the process of handling pen input relativeto a netpage. The process consists of receiving (at 884) a stroke fromthe pen; identifying (at 885) the page instance 830 to which the page ID50 in the stroke refers; retrieving (at 886) the page description 5;identifying (at 887) a formatted element 839 whose zone 58 the strokeintersects; determining (at 888) whether the formatted elementcorresponds to a field element, and if so appending (at 892) thereceived stroke to the digital ink of the field value 871, interpreting(at 893) the accumulated digital ink of the field, and determining (at894) whether the field is part of a hyperlinked group 866 and if soactivating (at 895) the associated hyperlink; alternatively determining(at 889) whether the formatted element corresponds to a hyperlinkelement and if so activating (at 895) the corresponding hyperlink;alternatively, in the absence of an input field or hyperlink, appending(at 890) the received stroke to the digital ink of the background field833; and copying (at 891) the received stroke to the current selection826 of the current pen, as maintained by the registration server.

FIG. 38 a shows a detailed flowchart of step 893 in the process shown inFIG. 38, where the accumulated digital ink of a field is interpretedaccording to the type of the field. The process consists of determining(at 896) whether the field is a checkbox and (at 897) whether thedigital ink represents a checkmark, and if so assigning (at 898) a truevalue to the field value; alternatively determining (at 899) whether thefield is a text field and if so converting (at 900) the digital ink tocomputer text, with the help of the appropriate registration server, andassigning (at 901) the converted computer text to the field value;alternatively determining (at 902) whether the field is a signaturefield and if so verifying (at 903) the digital ink as the signature ofthe pen's owner, with the help of the appropriate registration server,creating (at 904) a digital signature of the contents of thecorresponding form, also with the help of the registration server andusing the pen owner's private signature key relating to thecorresponding application, and assigning (at 905) the digital signatureto the field value.

1.7.3 Page Server Commands

A page server command is a command which is handled locally by the pageserver. It operates directly on form, page and document instances.

A page server command 907 can be a void form command 908, a duplicateform command 909, a reset form command 910, a get form status command911, a duplicate page command 912, a reset page command 913, a get pagestatus command 914, a duplicate document command 915, a reset documentcommand 916, or a get document status command 917, as shown in FIG. 39.

A void form command voids the corresponding form instance. A duplicateform command voids the corresponding form instance and then produces anactive printed copy of the current form instance with field valuespreserved. The copy contains the same hyperlink transaction IDs as theoriginal, and so is indistinguishable from the original to anapplication. A reset form command voids the corresponding form instanceand then produces an active printed copy of the form instance with fieldvalues discarded. A get form status command produces a printed report onthe status of the corresponding form instance, including who publishedit, when it was printed, for whom it was printed, and the form status ofthe form instance.

Since a form hyperlink instance contains a transaction ID, theapplication has to be involved in producing a new form instance. Abutton requesting a new form instance is therefore typically implementedas a hyperlink.

A duplicate page command produces a printed copy of the correspondingpage instance with the background field value preserved. If the pagecontains a form or is part of a form, then the duplicate page command isinterpreted as a duplicate form command. A reset page command produces aprinted copy of the corresponding page instance with the backgroundfield value discarded. If the page contains a form or is part of a form,then the reset page command is interpreted as a reset form command. Aget page status command produces a printed report on the status of thecorresponding page instance, including who published it, when it wasprinted, for whom it was printed, and the status of any forms itcontains or is part of.

The netpage logo which appears on every netpage is usually associatedwith a duplicate page element.

When a page instance is duplicated with field values preserved, fieldvalues are printed in their native form, i.e. a checkmark appears as astandard checkmark graphic, and text appears as typeset text. Onlydrawings and signatures appear in their original form, with a signatureaccompanied by a standard graphic indicating successful signatureverification.

A duplicate document command produces a printed copy of thecorresponding document instance with background field values preserved.If the document contains any forms, then the duplicate document commandduplicates the forms in the same way a duplicate form command does. Areset document command produces a printed copy of the correspondingdocument instance with background field values discarded. If thedocument contains any forms, then the reset document command resets theforms in the same way a reset form command does. A get document statuscommand produces a printed report on the status of the correspondingdocument instance, including who published it, when it was printed, forwhom it was printed, and the status of any forms it contains.

If the page server command's “on selected” attribute is set, then thecommand operates on the page identified by the pen's current selectionrather than on the page containing the command. This allows a menu ofpage server commands to be printed. If the target page doesn't contain apage server command element for the designated page server command, thenthe command is ignored.

An application can provide application-specific handling by embeddingthe relevant page server command element in a hyperlinked group. Thepage server activates the hyperlink associated with the hyperlinkedgroup rather than executing the page server command.

A page server command element is hidden if its “hidden” attribute isset. A hidden command element does not have an input zone on a page andso cannot be activated directly by a user. It can, however, be activatedvia a page server command embedded in a different page, if that pageserver command has its “on selected” attribute set.

1.8 Standard Features of Netpages

In the preferred form, each netpage is printed with the netpage logo atthe bottom to indicate that it is a netpage and therefore hasinteractive properties. The logo also acts as a copy button. In mostcases pressing the logo produces a copy of the page. In the case of aform, the button produces a copy of the entire form. And in the case ofa secure document, such as a ticket or coupon, the button elicits anexplanatory note or advertising page.

The default single-page copy function is handled directly by therelevant netpage page server. Special copy functions are handled bylinking the logo button to an application.

1.9 User Help System

In a preferred embodiment, the netpage printer has a single buttonlabelled “Help”. When pressed it elicits a single help page 46 ofinformation, including:

-   -   status of printer connection    -   status of printer consumables    -   top-level help menu    -   document function menu    -   top-level netpage network directory

The help menu provides a hierarchical manual on how to use the netpagesystem.

The document function menu includes the following functions:

-   -   print a copy of a document    -   print a clean copy of a form    -   print the status of a document

A document function is initiated by selecting the document and thenpressing the button. The status of a document indicates who published itand when, to whom it was delivered, and to whom and when it wassubsequently submitted as a form.

The help page is obviously unavailable if the printer is unable toprint. In this case the “error” light is lit and the user can requestremote diagnosis over the network.

2 Personalized Publication Model

In the following description, news is used as a canonical publicationexample to illustrate personalization mechanisms in the netpage system.Although news is often used in the limited sense of newspaper andnewsmagazine news, the intended scope in the present context is wider.

In the netpage system, the editorial content and the advertising contentof a news publication are personalized using different mechanisms. Theeditorial content is personalized according to the reader's explicitlystated and implicitly captured interest profile. The advertising contentis personalized according to the reader's locality and demographic.

2.1 Editorial Personalization

A subscriber can draw on two kinds of news sources: those that delivernews publications, and those that deliver news streams. While newspublications are aggregated and edited by the publisher, news streamsare aggregated either by a news publisher or by a specialized newsaggregator. News publications typically correspond to traditionalnewspapers and newsmagazines, while news streams can be many and varied:a “raw” news feed from a news service, a cartoon strip, a freelancewriter's column, a friend's bulletin board, or the reader's own e-mail.

The netpage publication server supports the publication of edited newspublications as well as the aggregation of multiple news streams. Byhandling the aggregation and hence the formatting of news streamsselected directly by the reader, the server is able to place advertisingon pages over which it otherwise has no editorial control.

The subscriber builds a daily newspaper by selecting one or morecontributing news publications, and creating a personalized version ofeach. The resulting daily editions are printed and bound together into asingle newspaper. The various members of a household typically expresstheir different interests and tastes by selecting different dailypublications and then customizing them.

For each publication, the reader optionally selects specific sections.Some sections appear daily, while others appear weekly. The dailysections available from The New York Times online, for example, include“Page One Plus”, “National”, “International”, “Opinion”, “Business”,“Arts/Living”, “Technology”, and “Sports”. The set of available sectionsis specific to a publication, as is the default subset.

The reader can extend the daily newspaper by creating custom sections,each one drawing on any number of news streams. Custom sections might becreated for e-mail and friends' announcements (“Personal”), or formonitoring news feeds for specific topics (“Alerts” or “Clippings”).

For each section, the reader optionally specifies its size, eitherqualitatively (e.g. short, medium, or long), or numerically (i.e. as alimit on its number of pages), and the desired proportion ofadvertising, either qualitatively (e.g. high, normal, low, none), ornumerically (i.e. as a percentage).

The reader also optionally expresses a preference for a large number ofshorter articles or a small number of longer articles. Each article isideally written (or edited) in both short and long forms to support thispreference.

An article may also be written (or edited) in different versions tomatch the expected sophistication of the reader, for example to providechildren's and adults' versions. The appropriate version is selectedaccording to the reader's age. The reader can specify a “reading age”which takes precedence over their biological age.

The articles which make up each section are selected and prioritized bythe editors, and each is assigned a useful lifetime. By default they aredelivered to all relevant subscribers, in priority order, subject tospace constraints in the subscribers' editions.

In sections where it is appropriate, the reader may optionally enablecollaborative filtering. This is then applied to articles which have asufficiently long lifetime. Each article which qualifies forcollaborative filtering is printed with rating buttons at the end of thearticle. The buttons can provide an easy choice (e.g. “liked” and“disliked”), making it more likely that readers will bother to rate thearticle.

Articles with high priorities and short lifetimes are thereforeeffectively considered essential reading by the editors and aredelivered to most relevant subscribers.

The reader optionally specifies a serendipity factor, eitherqualitatively (e.g. do or don't surprise me), or numerically. A highserendipity factor lowers the threshold used for matching duringcollaborative filtering. A high factor makes it more likely that thecorresponding section will be filled to the reader's specified capacity.A different serendipity factor can be specified for different days ofthe week.

The reader also optionally specifies topics of particular interestwithin a section, and this modifies the priorities assigned by theeditors.

The speed of the reader's Internet connection affects the quality atwhich images can be delivered. The reader optionally specifies apreference for fewer images or smaller images or both. If the number orsize of images is not reduced, then images may be delivered at lowerquality (i.e. at lower resolution or with greater compression).

At a global level, the reader specifies how quantities, dates, times andmonetary values are localized. This involves specifying whether unitsare imperial or metric, a local timezone and time format, and a localcurrency, and whether the localization consist of in situ translation orannotation. These preferences are derived from the reader's locality bydefault.

To reduce reading difficulties caused by poor eyesight, the readeroptionally specifies a global preference for a larger presentation. Bothtext and images are scaled accordingly, and less information isaccommodated on each page.

The language in which a news publication is published, and itscorresponding text encoding, is a property of the publication and not apreference expressed by the user. However, the netpage system can beconfigured to provide automatic translation services in various guises.

2.2 Advertising Localization and Targeting

The personalization of the editorial content directly affects theadvertising content, because advertising is typically placed to exploitthe editorial context. Travel ads, for example, are more likely toappear in a travel section than elsewhere. The value of the editorialcontent to an advertiser (and therefore to the publisher) lies in itsability to attract large numbers of readers with the right demographics.

Effective advertising is placed on the basis of locality anddemographics. Locality determines proximity to particular services,retailers etc., and particular interests and concerns associated withthe local community and environment. Demographics determine generalinterests and preoccupations as well as likely spending patterns.

A news publisher's most profitable product is advertising “space”, amulti-dimensional entity determined by the publication's geographiccoverage, the size of its readership, its readership demographics, andthe page area available for advertising.

In the netpage system, the netpage publication server computes theapproximate multi-dimensional size of a publication's saleableadvertising space on a per-section basis, taking into account thepublication's geographic coverage, the section's readership, the size ofeach reader's section edition, each reader's advertising proportion, andeach reader's demographic.

In comparison with other media, the netpage system allows theadvertising space to be defined in greater detail, and allows smallerpieces of it to be sold separately. It therefore allows it to be sold atcloser to its true value.

For example, the same advertising “slot” can be sold in varyingproportions to several advertisers, with individual readers' pagesrandomly receiving the advertisement of one advertiser or another,overall preserving the proportion of space sold to each advertiser.

The netpage system allows advertising to be linked directly to detailedproduct information and online purchasing. It therefore raises theintrinsic value of the advertising space.

Because personalization and localization are handled automatically bynetpage publication servers, an advertising aggregator can providearbitrarily broad coverage of both geography and demographics. Thesubsequent disaggregation is efficient because it is automatic. Thismakes it more cost-effective for publishers to deal with advertisingaggregators than to directly capture advertising. Even though theadvertising aggregator is taking a proportion of advertising revenue,publishers may find the change profit-neutral because of the greaterefficiency of aggregation. The advertising aggregator acts as anintermediary between advertisers and publishers, and may place the sameadvertisement in multiple publications.

It is worth noting that ad placement in a netpage publication can bemore complex than ad placement in the publication's traditionalcounterpart, because the publication's advertising space is morecomplex. While ignoring the full complexities of negotiations betweenadvertisers, advertising aggregators and publishers, the preferred formof the netpage system provides some automated support for thesenegotiations, including support for automated auctions of advertisingspace. Automation is particularly desirable for the placement ofadvertisements which generate small amounts of income, such as small orhighly localized advertisements.

Once placement has been negotiated, the aggregator captures and editsthe advertisement and records it on a netpage ad server.Correspondingly, the publisher records the ad placement on the relevantnetpage publication server. When the netpage publication server lays outeach user's personalized publication, it picks the relevantadvertisements from the netpage ad server.

2.3 User Profiles

2.3.1 Information Filtering

The personalization of news and other publications relies on anassortment of user-specific profile information, including:

-   -   publication customizations    -   collaborative filtering vectors    -   contact details    -   presentation preferences

The customization of a publication is typically publication-specific,and so the customization information is maintained by the relevantnetpage publication server.

A collaborative filtering vector consists of the user's ratings of anumber of news items. It is used to correlate different users' interestsfor the purposes of making recommendations. Although there are benefitsto maintaining a single collaborative filtering vector independently ofany particular publication, there are two reasons why it is morepractical to maintain a separate vector for each publication: there islikely to be more overlap between the vectors of subscribers to the samepublication than between those of subscribers to different publications;and a publication is likely to want to present its users' collaborativefiltering vectors as part of the value of its brand, not to be foundelsewhere. Collaborative filtering vectors are therefore also maintainedby the relevant netpage publication server.

Contact details, including name, street address, ZIP Code, state,country, telephone numbers, are global by nature, and are maintained bya netpage registration server.

Presentation preferences, including those for quantities, dates andtimes, are likewise global and maintained in the same way.

The localization of advertising relies on the locality indicated in theuser's contact details, while the targeting of advertising relies onpersonal information such as date of birth, gender, marital status,income, profession, education, or qualitative derivatives such as agerange and income range.

For those users who choose to reveal personal information foradvertising purposes, the information is maintained by the relevantnetpage registration server. In the absence of such information,advertising can be targeted on the basis of the demographic associatedwith the user's ZIP or ZIP+4 Code.

Each user, pen, printer, application provider and application isassigned its own unique identifier, and the netpage registration servermaintains the relationships between them, as shown in FIGS. 21, 22, 23and 24. For registration purposes, a publisher is a special kind ofapplication provider, and a publication is a special kind ofapplication.

Each user 800 may be authorized to use any number of printers 802, andeach printer may allow any number of users to use it. Each user has asingle default printer (at 66), to which periodical publications aredelivered by default, whilst pages printed on demand are delivered tothe printer through which the user is interacting. The server keepstrack of which publishers a user has authorized to print to the user'sdefault printer. A publisher does not record the ID of any particularprinter, but instead resolves the ID when it is required. The user mayalso be designated as having administrative privileges 69 on theprinter, allowing the user to authorize other users to use the printer.This only has meaning if the printer requires administrative privileges84 for such operations.

When a user subscribes 808 to a publication 807, the publisher 806 (i.e.application provider 803) is authorized to print to a specified printeror the user's default printer. This authorization can be revoked at anytime by the user. Each user may have several pens 801, but a pen isspecific to a single user. If a user is authorized to use a particularprinter, then that printer recognizes any of the user's pens.

The pen ID is used to locate the corresponding user profile maintainedby a particular netpage registration server, via the DNS in the usualway.

A Web terminal 809 can be authorized to print on a particular netpageprinter, allowing Web pages and netpage documents encountered during Webbrowsing to be conveniently printed on the nearest netpage printer.

The netpage system can collect, on behalf of a printer provider, feesand commissions on income earned through publications printed on theprovider's printers. Such income can include advertising fees,click-through fees, e-commerce commissions, and transaction fees. If theprinter is owned by the user, then the user is the printer provider.

Each user also has a netpage account 820 which is used to accumulatemicro-debits and credits (such as those described in the precedingparagraph); contact details 815, including name, address and telephonenumbers; global preferences 816, including privacy, delivery andlocalization settings; any number of biometric records 817, containingthe user's encoded signature 818, fingerprint 819 etc; a handwritingmodel 819 automatically maintained by the system; and SET payment cardaccounts 821, with which e-commerce payments can be made.

In addition to the user-specific netpage account, each user also has anetpage account 936 specific to each printer the user is authorized touse. Each printer-specific account is used to accumulate micro-debitsand credits related to the user's activities on that printer. The useris billed on a regular basis for any outstanding debit balances.

A user optionally appears in the netpage user directory 823, allowingother users to locate and direct e-mail (etc.) to the user.

2.4 Intelligent Page Layout

The netpage publication server automatically lays out the pages of eachuser's personalized publication on a section-by-section basis. Sincemost advertisements are in the form of pre-formatted rectangles, theyare placed on the page before the editorial content.

The advertising ratio for a section can be achieved with wildly varyingadvertising ratios on individual pages within the section, and the adlayout algorithm exploits this. The algorithm is configured to attemptto co-locate closely tied editorial and advertising content, such asplacing ads for roofing material specifically within the publicationbecause of a special feature on do-it-yourself roofing repairs.

The editorial content selected for the user, including text andassociated images and graphics, is then laid out according to variousaesthetic rules.

The entire process, including the selection of ads and the selection ofeditorial content, must be iterated once the layout has converged, toattempt to more closely achieve the user's stated section sizepreference. The section size preference can, however, be matched onaverage over time, allowing significant day-to-day variations.

2.5 Document Format

Once the document is laid out, it is encoded for efficient distributionand persistent storage on the netpage network.

The primary efficiency mechanism is the separation of informationspecific to a single user's edition and information shared betweenmultiple users' editions. The specific information consists of the pagelayout. The shared information consists of the objects to which the pagelayout refers, including images, graphics, and pieces of text.

A text object contains fully-formatted text represented in theExtensible Markup Language (XML) using the Extensible StylesheetLanguage (XSL). XSL provides precise control over text formattingindependently of the region into which the text is being set, which inthis case is being provided by the layout. The text object containsembedded language codes to enable automatic translation, and embeddedhyphenation hints to aid with paragraph formatting.

An image object encodes an image in the JPEG 2000 wavelet-basedcompressed image format. A graphic object encodes a 2D graphic inScalable Vector Graphics (SVG) format.

The layout itself consists of a series of placed image and graphicobjects, linked textflow objects through which text objects flow,hyperlinks and input fields as described above, and watermark regions.These layout objects are summarized in Table 3. The layout uses acompact format suitable for efficient distribution and storage.

TABLE 3 netpage layout objects Layout Format of object Attribute linkedobject image Position — Image object ID JPEG 2000 Graphic Position —Graphic object ID SVG Textflow Textflow ID — Zone — Optional text objectID XML/XSL Hyperlink Type — Zone — Application ID, etc. — Field Type —Meaning — Zone — Watermark Zone —2.6 Document Distribution

As described above, for purposes of efficient distribution andpersistent storage on the netpage network, a user-specific page layoutis separated from the shared objects to which it refers.

When a subscribed publication is ready to be distributed, the netpagepublication server allocates, with the help of the netpage ID server 12,a unique ID for each page, page instance, document, and documentinstance.

The server computes a set of optimized subsets of the shared content andcreates a multicast channel for each subset, and then tags eachuser-specific layout with the names of the multicast channels which willcarry the shared content used by that layout. The server then pointcastseach user's layouts to that user's printer via the appropriate pageserver, and when the pointcasting is complete, multicasts the sharedcontent on the specified channels. After receiving its pointcast, eachpage server and printer subscribes to the multicast channels specifiedin the page layouts. During the multicasts, each page server and printerextracts from the multicast streams those objects referred to by itspage layouts. The page servers persistently archive the received pagelayouts and shared content.

Once a printer has received all the objects to which its page layoutsrefer, the printer re-creates the fully-populated layout and thenrasterizes and prints it.

Under normal circumstances, the printer prints pages faster than theycan be delivered. Assuming a quarter of each page is covered withimages, the average page has a size of less than 400 KB. The printer cantherefore hold in excess of 100 such pages in its internal 64 MB memory,allowing for temporary buffers etc. The printer prints at a rate of onepage per second. This is equivalent to 400 KB or about 3 Mbit of pagedata per second, which is similar to the highest expected rate of pagedata delivery over a broadband network.

Even under abnormal circumstances, such as when the printer runs out ofpaper, it is likely that the user will be able to replenish the papersupply before the printer's 100-page internal storage capacity isexhausted.

However, if the printer's internal memory does fill up, then the printerwill be unable to make use of a multicast when it first occurs. Thenetpage publication server therefore allows printers to submit requestsfor re-multicasts. When a critical number of requests is received or atimeout occurs, the server re-multicasts the corresponding sharedobjects.

Once a document is printed, a printer can produce an exact duplicate atany time by retrieving its page layouts and contents from the relevantpage server.

2.7 On-Demand Documents

When a netpage document is requested on demand, it can be personalizedand delivered in much the same way as a periodical. However, since thereis no shared content, delivery is made directly to the requestingprinter without the use of multicast.

When a non-netpage document is requested on demand, it is notpersonalized, and it is delivered via a designated netpage formattingserver which reformats it as a netpage document. A netpage formattingserver is a special instance of a netpage publication server. Thenetpage formatting server has knowledge of various Internet documentformats, including Adobe's Portable Document Format (PDF), and HypertextMarkup Language (HTML). In the case of HTML, it can make use of thehigher resolution of the printed page to present Web pages in amulti-column format, with a table of contents. It can automaticallyinclude all Web pages directly linked to the requested page. The usercan tune this behavior via a preference.

The netpage formatting server makes standard netpage behavior, includinginteractivity and persistence, available on any Internet document, nomatter what its origin and format. It hides knowledge of differentdocument formats from both the netpage printer and the netpage pageserver, and hides knowledge of the netpage system from Web servers.

3 Security

3.1 Cryptography

Cryptography is used to protect sensitive information, both in storageand in transit, and to authenticate parties to a transaction. There aretwo classes of cryptography in widespread use: secret-key cryptographyand public-key cryptography. The netpage network uses both classes ofcryptography.

Secret-key cryptography, also referred to as symmetric cryptography,uses the same key to encrypt and decrypt a message. Two parties wishingto exchange messages must first arrange to securely exchange the secretkey.

Public-key cryptography, also referred to as asymmetric cryptography,uses two encryption keys. The two keys are mathematically related insuch a way that any message encrypted using one key can only bedecrypted using the other key. One of these keys is then published,while the other is kept private. The public key is used to encrypt anymessage intended for the holder of the private key. Once encrypted usingthe public key, a message can only be decrypted using the private key.Thus two parties can securely exchange messages without first having toexchange a secret key. To ensure that the private key is secure, it isnormal for the holder of the private key to generate the key pair.

Public-key cryptography can be used to create a digital signature. Theholder of the private key can create a known hash of a message and thenencrypt the hash using the private key. Anyone can then verify that theencrypted hash constitutes the “signature” of the holder of the privatekey with respect to that particular message by decrypting the encryptedhash using the public key and verifying the hash against the message. Ifthe signature is appended to the message, then the recipient of themessage can verify both that the message is genuine and that it has notbeen altered in transit.

To make public-key cryptography work, there has to be a way todistribute public keys which prevents impersonation. This is normallydone using certificates and certificate authorities. A certificateauthority is a trusted third party which authenticates the connectionbetween a public key and someone's identity. The certificate authorityverifies the person's identity by examining identity documents, and thencreates and signs a digital certificate containing the person's identitydetails and public key. Anyone who trusts the certificate authority canuse the public key in the certificate with a high degree of certaintythat it is genuine. They just have to verify that the certificate hasindeed been signed by the certificate authority, whose public key iswell-known.

In most transaction environments, public-key cryptography is only usedto create digital signatures and to securely exchange secret sessionkeys. Secret-key cryptography is used for all other purposes.

In the following discussion, when reference is made to the securetransmission of information between a netpage printer and a server, whatactually happens is that the printer obtains the server's certificate,authenticates it with reference to the certificate authority, uses thepublic key-exchange key in the certificate to exchange a secret sessionkey with the server, and then uses the secret session key to encrypt themessage data. A session key, by definition, can have an arbitrarilyshort lifetime.

3.2 Netpage Printer Security

Each netpage printer is assigned a pair of unique identifiers at time ofmanufacture which are stored in read-only memory in the printer and inthe netpage registration server database. The first ID 62 is public anduniquely identifies the printer on the netpage network. The second ID issecret and is used when the printer is first registered on the network.

When the printer connects to the netpage network for the first timeafter installation, it creates a signature public/private key pair. Ittransmits the secret ID and the public key securely to the netpageregistration server. The server compares the secret ID against theprinter's secret ID recorded in its database, and accepts theregistration if the IDs match. It then creates and signs a certificatecontaining the printer's public ID and public signature key, and storesthe certificate in the registration database.

The netpage registration server acts as a certificate authority fornetpage printers, since it has access to secret information allowing itto verify printer identity.

When a user subscribes to a publication, a record is created in thenetpage registration server database authorizing the publisher to printthe publication to the user's default printer or a specified printer.Every document sent to a printer via a page server is addressed to aparticular user and is signed by the publisher using the publisher'sprivate signature key. The page server verifies, via the registrationdatabase, that the publisher is authorized to deliver the publication tothe specified user. The page server verifies the signature using thepublisher's public key, obtained from the publisher's certificate storedin the registration database.

The netpage registration server accepts requests to add printingauthorizations to the database, so long as those requests are initiatedvia a pen registered to the printer.

3.3 Netpage Pen Security

Each netpage pen is assigned a unique identifier at time of manufacturewhich is stored in read-only memory in the pen and in the netpageregistration server database. The pen ID 61 uniquely identifies the penon the netpage network.

A netpage pen can “know” a number of netpage printers, and a printer can“know” a number of pens. A pen communicates with a printer via a radiofrequency signal whenever it is within range of the printer. Once a penand printer are registered, they regularly exchange session keys.Whenever the pen transmits digital ink to the printer, the digital inkis always encrypted using the appropriate session key. Digital ink isnever transmitted in the clear.

A pen stores a session key for every printer it knows, indexed byprinter ID, and a printer stores a session key for every pen it knows,indexed by pen ID. Both have a large but finite storage capacity forsession keys, and will forget a session key on a least-recently-usedbasis if necessary.

When a pen comes within range of a printer, the pen and printer discoverwhether they know each other. If they don't know each other, then theprinter determines whether it is supposed to know the pen. This mightbe, for example, because the pen belongs to a user who is registered touse the printer. If the printer is meant to know the pen but doesn't,then it initiates the automatic pen registration procedure. If theprinter isn't meant to know the pen, then it agrees with the pen toignore it until the pen is placed in a charging cup, at which time itinitiates the registration procedure.

In addition to its public ID, the pen contains a secret key-exchangekey. The key-exchange key is also recorded in the netpage registrationserver database at time of manufacture. During registration, the pentransmits its pen ID to the printer, and the printer transmits the penID to the netpage registration server. The server generates a sessionkey for the printer and pen to use, and securely transmits the sessionkey to the printer. It also transmits a copy of the session keyencrypted with the pen's key-exchange key. The printer stores thesession key internally, indexed by the pen ID, and transmits theencrypted session key to the pen. The pen stores the session keyinternally, indexed by the printer ID.

Although a fake pen can impersonate a pen in the pen registrationprotocol, only a real pen can decrypt the session key transmitted by theprinter.

When a previously unregistered pen is first registered, it is of limiteduse until it is linked to a user. A registered but “un-owned” pen isonly allowed to be used to request and fill in netpage user and penregistration forms, to register a new user to which the new pen isautomatically linked, or to add a new pen to an existing user.

The pen uses secret-key rather than public-key encryption because ofhardware performance constraints in the pen.

3.4 Secure Documents

The netpage system supports the delivery of secure documents such astickets and coupons. The netpage printer includes a facility to printwatermarks, but will only do so on request from publishers who aresuitably authorized. The publisher indicates its authority to printwatermarks in its certificate, which the printer is able toauthenticate.

The “watermark” printing process uses an alternative dither matrix inspecified “watermark” regions of the page. Back-to-back pages containmirror-image watermark regions which coincide when printed. The dithermatrices used in odd and even pages' watermark regions are designed toproduce an interference effect when the regions are viewed together,achieved by looking through the printed sheet.

The effect is similar to a watermark in that it is not visible whenlooking at only one side of the page, and is lost when the page iscopied by normal means.

Pages of secure documents cannot be copied using the built-in netpagecopy mechanism described in Section 1.9 above. This extends to copyingnetpages on netpage-aware photocopiers.

Secure documents are typically generated as part of e-commercetransactions. They can therefore include the user's photograph which wascaptured when the user registered biometric information with the netpageregistration server, as described in Section 2.

When presented with a secure netpage document, the recipient can verifyits authenticity by requesting its status in the usual way. The uniqueID of a secure document is only valid for the lifetime of the document,and secure document IDs are allocated non-contiguously to prevent theirprediction by opportunistic forgers. A secure document verification pencan be developed with built-in feedback on verification failure, tosupport easy point-of-presentation document verification.

Clearly neither the watermark nor the user's photograph are secure in acryptographic sense. They simply provide a significant obstacle tocasual forgery. Online document verification, particularly using averification pen, provides an added level of security where it isneeded, but is still not entirely immune to forgeries.

3.5 Non-Repudiation

In the netpage system, forms submitted by users are delivered reliablyto forms handlers and are persistently archived on netpage page servers.It is therefore impossible for recipients to repudiate delivery.

E-commerce payments made through the system, as described in Section 4,are also impossible for the payee to repudiate.

4 Electronic Commerce Model

4.1 Secure Electronic Transaction (SET)

The netpage system uses the Secure Electronic Transaction (SET) systemas one of its payment systems. SET, having been developed by MasterCardand Visa, is organized around payment cards, and this is reflected inthe terminology. However, much of the system is independent of the typeof accounts being used.

In SET, cardholders and merchants register with a certificate authorityand are issued with certificates containing their public signature keys.The certificate authority verifies a cardholder's registration detailswith the card issuer as appropriate, and verifies a merchant'sregistration details with the acquirer as appropriate. Cardholders andmerchants store their respective private signature keys securely ontheir computers. During the payment process, these certificates are usedto mutually authenticate a merchant and cardholder, and to authenticatethem both to the payment gateway.

SET has not yet been adopted widely, partly because cardholdermaintenance of keys and certificates is considered burdensome. Interimsolutions which maintain cardholder keys and certificates on a serverand give the cardholder access via a password have met with somesuccess.

4.2 SET Payments

In the netpage system the netpage registration server acts as a proxyfor the netpage user (i.e. the cardholder) in SET payment transactions.

The netpage system uses biometrics to authenticate the user andauthorize SET payments. Because the system is pen-based, the biometricused is the user's on-line signature, consisting of time-varying penposition and pressure. A fingerprint biometric can also be used bydesigning a fingerprint sensor into the pen, although at a higher cost.The type of biometric used only affects the capture of the biometric,not the authorization aspects of the system.

The first step to being able to make SET payments is to register theuser's biometric with the netpage registration server. This is done in acontrolled environment, for example a bank, where the biometric can becaptured at the same time as the user's identity is verified. Thebiometric is captured and stored in the registration database, linked tothe user's record. The user's photograph is also optionally captured andlinked to the record. The SET cardholder registration process iscompleted, and the resulting private signature key and certificate arestored in the database. The user's payment card information is alsostored, giving the netpage registration server enough information to actas the user's proxy in any SET payment transaction.

When the user eventually supplies the biometric to complete a payment,for example by signing a netpage order form, the printer securelytransmits the order information, the pen ID and the biometric data tothe netpage registration server. The server verifies the biometric withrespect to the user identified by the pen ID, and from then on acts asthe user's proxy in completing the SET payment transaction.

4.3 Micro-Payments

The netpage system includes a mechanism for micro-payments, to allow theuser to be conveniently charged for printing low-cost documents ondemand and for copying copyright documents, and possibly also to allowthe user to be reimbursed for expenses incurred in printing advertisingmaterial. The latter depends on the level of subsidy already provided tothe user.

When the user registers for e-commerce, a network account is establishedwhich aggregates micro-payments. The user receives a statement on aregular basis, and can settle any outstanding debit balance using thestandard payment mechanism.

The network account can be extended to aggregate subscription fees forperiodicals, which would also otherwise be presented to the user in theform of individual statements.

4.4 Transactions

When a user requests a netpage in a particular application context, theapplication is able to embed a user-specific transaction ID 55 in thepage. Subsequent input through the page is tagged with the transactionID, and the application is thereby able to establish an appropriatecontext for the user's input.

When input occurs through a page which is not user-specific, however,the application must use the user's unique identity to establish acontext. A typical example involves adding items from a pre-printedcatalog page to the user's virtual “shopping cart”. To protect theuser's privacy, however, the unique user ID 60 known to the netpagesystem is not divulged to applications. This is to prevent differentapplication providers from easily correlating independently accumulatedbehavioral data.

The netpage registration server instead maintains an anonymousrelationship between a user and an application via a unique alias ID 65,as shown in FIG. 24. Whenever the user activates a hyperlink tagged withthe “registered” attribute, the netpage page server asks the netpageregistration server to translate the associated application ID 64,together with the pen ID 61, into an alias ID 65. The alias ID is thensubmitted to the hyperlink's application.

The application maintains state information indexed by alias ID, and isable to retrieve user-specific state information without knowledge ofthe global identity of the user.

The system also maintains an independent certificate and privatesignature key for each of a user's applications, to allow it to signapplication transactions on behalf of the user using onlyapplication-specific information.

To assist the system in routing product bar code (UPC) “hyperlink”activations, the system records a favorite application on behalf of theuser for any number of product types.

Each application is associated with an application provider, and thesystem maintains an account on behalf of each application provider, toallow it to credit and debit the provider for click-through fees etc.

An application provider can be a publisher of periodical subscribedcontent. The system records the user's willingness to receive thesubscribed publication, as well as the expected frequency ofpublication.

5 Communications Protocols

A communications protocol defines an ordered exchange of messagesbetween entities. In the netpage system, entities such as pens, printersand servers utilise a set of defined protocols to cooperatively handleuser interaction with the netpage system.

Each protocol is illustrated by way of a sequence diagram in which thehorizontal dimension is used to represent message flow and the verticaldimension is used to represent time. Each entity is represented by arectangle containing the name of the entity and a vertical columnrepresenting the lifeline of the entity. During the time an entityexists, the lifeline is shown as a dashed line. During the time anentity is active, the lifeline is shown as a double line. Because theprotocols considered here do not create or destroy entities, lifelinesare generally cut short as soon as an entity ceases to participate in aprotocol.

5.1 Subscription Delivery Protocol

A preferred embodiment of a subscription delivery protocol is shown inFIG. 40.

A large number of users may subscribe to a periodical publication. Eachuser's edition may be laid out differently, but many users' editionswill share common content such as text objects and image objects. Thesubscription delivery protocol therefore delivers document structures toindividual printers via pointcast, but delivers shared content objectsvia multicast.

The application (i.e. publisher) first obtains a document ID 51 for eachdocument from an ID server 12. It then sends each document structure,including its document ID and page descriptions, to the page server 10responsible for the document's newly allocated ID. It includes its ownapplication ID 64, the subscriber's alias ID 65, and the relevant set ofmulticast channel names. It signs the message using its privatesignature key.

The page server uses the application ID and alias ID to obtain from theregistration server the corresponding user ID 60, the user's selectedprinter ID 62 (which may be explicitly selected for the application, ormay be the user's default printer), and the application's certificate.

The application's certificate allows the page server to verify themessage signature. The page server's request to the registration serverfails if the application ID and alias ID don't together identify asubscription 808.

The page server then allocates document and page instance IDs andforwards the page descriptions, including page IDs 50, to the printer.It includes the relevant set of multicast channel names for the printerto listen to.

It then returns the newly allocated page IDs to the application forfuture reference.

Once the application has distributed all of the document structures tothe subscribers' selected printers via the relevant page servers, itmulticasts the various subsets of the shared objects on the previouslyselected multicast channels. Both page servers and printers monitor theappropriate multicast channels and receive their required contentobjects. They are then able to populate the previously pointcastdocument structures. This allows the page servers to add completedocuments to their databases, and it allows the printers to print thedocuments.

5.2 Hyperlink Activation Protocol

A preferred embodiment of a hyperlink activation protocol is shown inFIG. 42.

When a user clicks on a netpage with a netpage pen, the pen communicatesthe click to the nearest netpage printer 601. The click identifies thepage and a location on the page. The printer already knows the ID 61 ofthe pen from the pen connection protocol.

The printer determines, via the DNS, the network address of the pageserver 10 a handling the particular page ID 50. The address may alreadybe in its cache if the user has recently interacted with the same page.The printer then forwards the pen ID, its own printer ID 62, the page IDand click location to the page server.

The page server loads the page description 5 identified by the page IDand determines which input element's zone 58, if any, the click lies in.Assuming the relevant input element is a hyperlink element 844, the pageserver then obtains the associated application ID 64 and link ID 54, anddetermines, via the DNS, the network address of the application serverhosting the application 71.

The page server uses the pen ID 61 to obtain the corresponding user ID60 from the registration server 11, and then allocates a globally uniquehyperlink request ID 52 and builds a hyperlink request 934. Thehyperlink request class diagram is shown in FIG. 41. The hyperlinkrequest records the IDs of the requesting user and printer, andidentifies the clicked hyperlink instance 862. The page server thensends its own server ID 53, the hyperlink request ID, and the link ID tothe application.

The application produces a response document according toapplication-specific logic, and obtains a document ID 51 from an IDserver 12. It then sends the document to the page server 10 bresponsible for the document's newly allocated ID, together with therequesting page server's ID and the hyperlink request ID.

The second page server sends the hyperlink request ID and application IDto the first page server to obtain the corresponding user ID and printerID 62. The first page server rejects the request if the hyperlinkrequest has expired or is for a different application.

The second page server allocates document instance and page IDs 50,returns the newly allocated page IDs to the application, adds thecomplete document to its own database, and finally sends the pagedescriptions to the requesting printer.

The hyperlink instance may include a meaningful transaction ID 55, inwhich case the first page server includes the transaction ID in themessage sent to the application. This allows the application toestablish a transaction-specific context for the hyperlink activation.

If the hyperlink requires a user alias, i.e. its “alias required”attribute is set, then the first page server sends both the pen ID 61and the hyperlink's application ID 64 to the registration server 11 toobtain not just the user ID corresponding to the pen ID but also thealias ID 65 corresponding to the application ID and the user ID. Itincludes the alias ID in the message sent to the application, allowingthe application to establish a user-specific context for the hyperlinkactivation.

5.3 Handwriting Recognition Protocol

When a user draws a stroke on a netpage with a netpage pen, the pencommunicates the stroke to the nearest netpage printer. The strokeidentifies the page and a path on the page.

The printer forwards the pen ID 61, its own printer ID 62, the page ID50 and stroke path to the page server 10 in the usual way.

The page server loads the page description 5 identified by the page IDand determines which input element's zone 58, if any, the strokeintersects. Assuming the relevant input element is a text field 878, thepage server appends the stroke to the text field's digital ink.

After a period of inactivity in the zone of the text field, the pageserver sends the pen ID and the pending strokes to the registrationserver 11 for interpretation. The registration server identifies theuser corresponding to the pen, and uses the user's accumulatedhandwriting model 822 to interpret the strokes as handwritten text. Onceit has converted the strokes to text, the registration server returnsthe text to the requesting page server. The page server appends the textto the text value of the text field.

5.4 Signature Verification Protocol

Assuming the input element whose zone the stroke intersects is asignature field 880, the page server 10 appends the stroke to thesignature field's digital ink.

After a period of inactivity in the zone of the signature field, thepage server sends the pen ID 61 and the pending strokes to theregistration server 11 for verification. It also sends the applicationID 64 associated with the form of which the signature field is part, aswell as the form ID 56 and the current data content of the form. Theregistration server identifies the user corresponding to the pen, anduses the user's dynamic signature biometric 818 to verify the strokes asthe user's signature. Once it has verified the signature, theregistration server uses the application ID 64 and user ID 60 toidentify the user's application-specific private signature key. It thenuses the key to generate a digital signature of the form data, andreturns the digital signature to the requesting page server. The pageserver assigns the digital signature to the signature field and sets theassociated form's status to frozen.

The digital signature includes the alias ID 65 of the correspondinguser. This allows a single form to capture multiple users' signatures.

5.5 Form Submission Protocol

A preferred embodiment of a form submission protocol is shown in FIG.43.

Form submission occurs via a form hyperlink activation. It thus followsthe protocol defined in Section 5.2, with some form-specific additions.

In the case of a form hyperlink, the hyperlink activation message sentby the page server 10 to the application 71 also contains the form ID 56and the current data content of the form. If the form contains anysignature fields, then the application verifies each one by extractingthe alias ID 65 associated with the corresponding digital signature andobtaining the corresponding certificate from the registration server 11.

6 Netpage Pen Description

6.1 Pen Mechanics

Referring to FIGS. 8 and 9, the pen, generally designated by referencenumeral 101, includes a housing 102 in the form of a plastics mouldinghaving walls 103 defining an interior space 104 for mounting the pencomponents. The pen top 105 is in operation rotatably mounted at one end106 of the housing 102. A semi-transparent cover 107 is secured to theopposite end 108 of the housing 102. The cover 107 is also of mouldedplastics, and is formed from semi-transparent material in order toenable the user to view the status of the LED mounted within the housing102. The cover 107 includes a main part 109 which substantiallysurrounds the end 108 of the housing 102 and a projecting portion 110which projects back from the main part 109 and fits within acorresponding slot 111 formed in the walls 103 of the housing 102. Aradio antenna 112 is mounted behind the projecting portion 110, withinthe housing 102. Screw threads 113 surrounding an aperture 113A on thecover 107 are arranged to receive a metal end piece 114, includingcorresponding screw threads 115. The metal end piece 114 is removable toenable ink cartridge replacement.

Also mounted within the cover 107 is a tri-color status LED 116 on aflex PCB 117. The antenna 112 is also mounted on the flex PCB 117. Thestatus LED 116 is mounted at the top of the pen 101 for good all-aroundvisibility.

The pen can operate both as a normal marking ink pen and as anon-marking stylus. An ink pen cartridge 118 with nib 119 and a stylus120 with stylus nib 121 are mounted side by side within the housing 102.Either the ink cartridge nib 119 or the stylus nib 121 can be broughtforward through open end 122 of the metal end piece 114, by rotation ofthe pen top 105. Respective slider blocks 123 and 124 are mounted to theink cartridge 118 and stylus 120, respectively. A rotatable cam barrel125 is secured to the pen top 105 in operation and arranged to rotatetherewith. The cam barrel 125 includes a cam 126 in the form of a slotwithin the walls 181 of the cam barrel. Cam followers 127 and 128projecting from slider blocks 123 and 124 fit within the cam slot 126.On rotation of the cam barrel 125, the slider blocks 123 or 124 moverelative to each other to project either the pen nib 119 or stylus nib121 out through the hole 122 in the metal end piece 114. The pen 101 hasthree states of operation. By turning the top 105 through 90° steps, thethree states are:

-   -   Stylus 120 nib 121 out;    -   Ink cartridge 118 nib 119 out; and    -   Neither ink cartridge 118 nib 119 out nor stylus 120 nib 121        out.

A second flex PCB 129, is mounted on an electronics chassis 130 whichsits within the housing 102. The second flex PCB 129 mounts an infraredLED 131 for providing infrared radiation for projection onto thesurface. An image sensor 132 is provided mounted on the second flex PCB129 for receiving reflected radiation from the surface. The second flexPCB 129 also mounts a radio frequency chip 133, which includes an RFtransmitter and RF receiver, and a controller chip 134 for controllingoperation of the pen 101. An optics block 135 (formed from moulded clearplastics) sits within the cover 107 and projects an infrared beam ontothe surface and receives images onto the image sensor 132. Power supplywires 136 connect the components on the second flex PCB 129 to batterycontacts 137 which are mounted within the cam barrel 125. A terminal 138connects to the battery contacts 137 and the cam barrel 125. A threevolt rechargeable battery 139 sits within the cam barrel 125 in contactwith the battery contacts. An induction charging coil 140 is mountedabout the second flex PCB 129 to enable recharging of the battery 139via induction. The second flex PCB 129 also mounts an infrared LED 143and infrared photodiode 144 for detecting displacement in the cam barrel125 when either the stylus 120 or the ink cartridge 118 is used forwriting, in order to enable a determination of the force being appliedto the surface by the pen nib 119 or stylus nib 121. The IR photodiode144 detects light from the IR LED 143 via reflectors (not shown) mountedon the slider blocks 123 and 124.

Rubber grip pads 141 and 142 are provided towards the end 108 of thehousing 102 to assist gripping the pen 101, and top 105 also includes aclip 142 for clipping the pen 101 to a pocket.

6.2 Pen Controller

The pen 101 is arranged to determine the position of its nib (stylus nib121 or ink cartridge nib 119) by imaging, in the infrared spectrum, anarea of the surface in the vicinity of the nib. It records the locationdata from the nearest location tag, and is arranged to calculate thedistance of the nib 121 or 119 from the location tab utilising optics135 and controller chip 134. The controller chip 134 calculates theorientation of the pen and the nib-to-tag distance from the perspectivedistortion observed on the imaged tag.

Utilising the RF chip 133 and antenna 112 the pen 101 can transmit thedigital ink data (which is encrypted for security and packaged forefficient transmission) to the computing system.

When the pen is in range of a receiver, the digital ink data istransmitted as it is formed. When the pen 101 moves out of range,digital ink data is buffered within the pen 101 (the pen 101 circuitryincludes a buffer arranged to store digital ink data for approximately12 minutes of the pen motion on the surface) and can be transmittedlater.

The controller chip 134 is mounted on the second flex PCB 129 in the pen101. FIG. 10 is a block diagram illustrating in more detail thearchitecture of the controller chip 134. FIG. 10 also showsrepresentations of the RF chip 133, the image sensor 132, the tri-colorstatus LED 116, the IR illumination LED 131, the IR force sensor LED143, and the force sensor photodiode 144.

The pen controller chip 134 includes a controlling processor 145. Bus146 enables the exchange of data between components of the controllerchip 134. Flash memory 147 and a 512 KB DRAM 148 are also included. Ananalog-to-digital converter 149 is arranged to convert the analog signalfrom the force sensor photodiode 144 to a digital signal.

An image sensor interface 152 interfaces with the image sensor 132. Atransceiver controller 153 and base band circuit 154 are also includedto interface with the RF chip 133 which includes an RF circuit 155 andRF resonators and inductors 156 connected to the antenna 112.

The controlling processor 145 captures and decodes location data fromtags from the surface via the image sensor 132, monitors the forcesensor photodiode 144, controls the LEDs 116, 131 and 143, and handlesshort-range radio communication via the radio transceiver 153. It is amedium-performance (˜40 MHz) general-purpose RISC processor.

The processor 145, digital transceiver components (transceivercontroller 153 and baseband circuit 154), image sensor interface 152,flash memory 147 and 512 KB DRAM 148 are integrated in a singlecontroller ASIC. Analog RF components (RF circuit 155 and RF resonatorsand inductors 156) are provided in the separate RF chip.

The image sensor is a 215×215 pixel CCD (such a sensor is produced byMatsushita Electronic Corporation, and is described in a paper byItakura, K T Nobusada, N Okusenya, R Nagayoshi, and M Ozaki, “A 1 mm 50k-Pixel IT CCD Image Sensor for Miniature Camera System”, IEEETransactions on Electronic Devices, Volt 47, number 1, January 2000,which is incorporated herein by reference) with an IR filter.

The controller ASIC 134 enters a quiescent state after a period ofinactivity when the pen 101 is not in contact with a surface. Itincorporates a dedicated circuit 150 which monitors the force sensorphotodiode 144 and wakes up the controller 134 via the power manager 151on a pen-down event.

The radio transceiver communicates in the unlicensed 900 MHz bandnormally used by cordless telephones, or alternatively in the unlicensed2.4 GHz industrial, scientific and medical (ISM) band, and usesfrequency hopping and collision detection to provide interference-freecommunication.

In an alternative embodiment, the pen incorporates an Infrared DataAssociation (IrDA) interface for short-range communication with a basestation or netpage printer.

In a further embodiment, the pen 101 includes a pair of orthogonalaccelerometers mounted in the normal plane of the pen 101 axis. Theaccelerometers 190 are shown in FIGS. 9 and 10 in ghost outline.

The provision of the accelerometers enables this embodiment of the pen101 to sense motion without reference to surface location tags, allowingthe location tags to be sampled at a lower rate. Each location tag IDcan then identify an object of interest rather than a position on thesurface. For example, if the object is a user interface input element(e.g. a command button), then the tag ID of each location tag within thearea of the input element can directly identify the input element.

The acceleration measured by the accelerometers in each of the x and ydirections is integrated with respect to time to produce aninstantaneous velocity and position.

Since the starting position of the stroke is not known, only relativepositions within a stroke are calculated. Although position integrationaccumulates errors in the sensed acceleration, accelerometers typicallyhave high resolution, and the time duration of a stroke, over whicherrors accumulate, is short.

7 Netpage Printer Description

7.1 Printer Mechanics

The vertically-mounted netpage wallprinter 601 is shown fully assembledin FIG. 11. It prints netpages on Letter/A4 sized media using duplexed8½″ Memjet™ print engines 602 and 603, as shown in FIGS. 12 and 12 a. Ituses a straight paper path with the paper 604 passing through theduplexed print engines 602 and 603 which print both sides of a sheetsimultaneously, in full color and with full bleed.

An integral binding assembly 605 applies a strip of glue along one edgeof each printed sheet, allowing it to adhere to the previous sheet whenpressed against it. This creates a final bound document 618 which canrange in thickness from one sheet to several hundred sheets.

The replaceable ink cartridge 627, shown in FIG. 13 coupled with theduplexed print engines, has bladders or chambers for storing fixative,adhesive, and cyan, magenta, yellow, black and infrared inks. Thecartridge also contains a micro air filter in a base molding. The microair filter interfaces with an air pump 638 inside the printer via a hose639. This provides filtered air to the printheads to prevent ingress ofmicro particles into the Memjet™ printheads 350 which might otherwiseclog the printhead nozzles. By incorporating the air filter within thecartridge, the operational life of the filter is effectively linked tothe life of the cartridge. The ink cartridge is a fully recyclableproduct with a capacity for printing and gluing 3000 pages (1500sheets).

Referring to FIG. 12, the motorized media pick-up roller assembly 626pushes the top sheet directly from the media tray past a paper sensor onthe first print engine 602 into the duplexed Memjet™ printhead assembly.The two Memjet™ print engines 602 and 603 are mounted in an opposingin-line sequential configuration along the straight paper path. Thepaper 604 is drawn into the first print engine 602 by integral, poweredpick-up rollers 626. The position and size of the paper 604 is sensedand full bleed printing commences. Fixative is printed simultaneously toaid drying in the shortest possible time.

The paper exits the first Memjet™ print engine 602 through a set ofpowered exit spike wheels (aligned along the straight paper path), whichact against a rubberized roller. These spike wheels contact the ‘wet’printed surface and continue to feed the sheet 604 into the secondMemjet™ print engine 603.

Referring to FIGS. 12 and 12 a, the paper 604 passes from the duplexedprint engines 602 and 603 into the binder assembly 605. The printed pagepasses between a powered spike wheel axle 670 with a fibrous supportroller and another movable axle with spike wheels and a momentary actionglue wheel. The movable axle/glue assembly 673 is mounted to a metalsupport bracket and it is transported forward to interface with thepowered axle 670 via gears by action of a camshaft. A separate motorpowers this camshaft.

The glue wheel assembly 673 consists of a partially hollow axle 679 witha rotating coupling for the glue supply hose 641 from the ink cartridge627. This axle 679 connects to a glue wheel, which absorbs adhesive bycapillary action through radial holes. A molded housing 682 surroundsthe glue wheel, with an opening at the front. Pivoting side moldings andsprung outer doors are attached to the metal bracket and hinge outsideways when the rest of the assembly 673 is thrust forward. Thisaction exposes the glue wheel through the front of the molded housing682. Tension springs close the assembly and effectively cap the gluewheel during periods of inactivity.

As the sheet 604 passes into the glue wheel assembly 673, adhesive isapplied to one vertical edge on the front side (apart from the firstsheet of a document) as it is transported down into the binding assembly605.

7.2 Printer Controller Architecture

The netpage printer controller consists of a controlling processor 750,a factory-installed or field-installed network interface module 625, aradio transceiver (transceiver controller 753, baseband circuit 754, RFcircuit 755, and RF resonators and inductors 756), dual raster imageprocessor (RIP) DSPs 757, duplexed print engine controllers 760 a and760 b, flash memory 658, and 64 MB of DRAM 657, as illustrated in FIG.14.

The controlling processor handles communication with the network 19 andwith local wireless netpage pens 101, senses the help button 617,controls the user interface LEDs 613-616, and feeds and synchronizes theRIP DSPs 757 and print engine controllers 760. It consists of amedium-performance general-purpose microprocessor. The controllingprocessor 750 communicates with the print engine controllers 760 via ahigh-speed serial bus 659.

The RIP DSPs rasterize and compress page descriptions to the netpageprinter's compressed page format. Each print engine controller expands,dithers and prints page images to its associated Memjet™ printhead 350in real time (i.e. at over 30 pages per minute). The duplexed printengine controllers print both sides of a sheet simultaneously.

The master print engine controller 760 a controls the paper transportand monitors ink usage in conjunction with the master QA chip 665 andthe ink cartridge QA chip 761.

The printer controller's flash memory 658 holds the software for boththe processor 750 and the DSPs 757, as well as configuration data. Thisis copied to main memory 657 at boot time.

The processor 750, DSPs 757, and digital transceiver components(transceiver controller 753 and baseband circuit 754) are integrated ina single controller ASIC 656. Analog RF components (RF circuit 755 andRF resonators and inductors 756) are provided in a separate RF chip 762.The network interface module 625 is separate, since netpage printersallow the network connection to be factory-selected or field-selected.Flash memory 658 and the 2×256 Mbit (64 MB) DRAM 657 is also off-chip.The print engine controllers 760 are provided in separate ASICs.

A variety of network interface modules 625 are provided, each providinga netpage network interface 751 and optionally a local computer ornetwork interface 752. Netpage network Internet interfaces include POTSmodems, Hybrid Fiber-Coax (HFC) cable modems, ISDN modems, DSL modems,satellite transceivers, current and next-generation cellular telephonetransceivers, and wireless local loop (WLL) transceivers. Localinterfaces include IEEE 1284 (parallel port), 10Base-T and 100Base-TEthernet, USB and USB 2.0, IEEE 1394 (Firewire), and various emerginghome networking interfaces. If an Internet connection is available onthe local network, then the local network interface can be used as thenetpage network interface.

The radio transceiver 753 communicates in the unlicensed 900 MHz bandnormally used by cordless telephones, or alternatively in the unlicensed2.4 GHz industrial, scientific and medical (ISM) band, and usesfrequency hopping and collision detection to provide interference-freecommunication.

The printer controller optionally incorporates an Infrared DataAssociation (IrDA) interface for receiving data “squirted” from devicessuch as netpage cameras. In an alternative embodiment, the printer usesthe IrDA interface for short-range communication with suitablyconfigured netpage pens.

7.2.1 Rasterization and Printing

Once the main processor 750 has received and verified the document'spage layouts and page objects, it runs the appropriate RIP software onthe DSPs 757.

The DSPs 757 rasterize each page description and compress the rasterizedpage image. The main processor stores each compressed page image inmemory. The simplest way to load-balance multiple DSPs is to let eachDSP rasterize a separate page. The DSPs can always be kept busy since anarbitrary number of rasterized pages can, in general, be stored inmemory. This strategy only leads to potentially poor DSP utilizationwhen rasterizing short documents.

Watermark regions in the page description are rasterized to acontone-resolution bi-level bitmap which is losslessly compressed tonegligible size and which forms part of the compressed page image.

The infrared (IR) layer of the printed page contains coded netpage tagsat a density of about six per inch. Each tag encodes the page ID, tagID, and control bits, and the data content of each tag is generatedduring rasterization and stored in the compressed page image.

The main processor 750 passes back-to-back page images to the duplexedprint engine controllers 760. Each print engine controller 760 storesthe compressed page image in its local memory, and starts the pageexpansion and printing pipeline. Page expansion and printing ispipelined because it is impractical to store an entire 114 MB bi-levelCMYK+IR page image in memory.

7.2.2 Print Engine Controller

The page expansion and printing pipeline of the print engine controller760 consists of a high speed IEEE 1394 serial interface 659, a standardJPEG decoder 763, a standard Group 4 Fax decoder 764, a customhalftoner/compositor unit 765, a custom tag encoder 766, a lineloader/formatter unit 767, and a custom interface 768 to the Memjet™printhead 350.

The print engine controller 360 operates in a double buffered manner.While one page is loaded into DRAM 769 via the high speed serialinterface 659, the previously loaded page is read from DRAM 769 andpassed through the print engine controller pipeline. Once the page hasfinished printing, the page just loaded is printed while another page isloaded.

The first stage of the pipeline expands (at 763) the JPEG-compressedcontone CMYK layer, expands (at 764) the Group 4 Fax-compressed bi-levelblack layer, and renders (at 766) the bi-level netpage tag layeraccording to the tag format defined in section 1.2, all in parallel. Thesecond stage dithers (at 765) the contone CMYK layer and composites (at765) the bi-level black layer over the resulting bi-level CMYK layer.The resultant bi-level CMYK+IR dot data is buffered and formatted (at767) for printing on the Memjet™ printhead 350 via a set of linebuffers. Most of these line buffers are stored in the off-chip DRAM. Thefinal stage prints the six channels of bi-level dot data (includingfixative) to the Memjet™ printhead 350 via the printhead interface 768.

When several print engine controllers 760 are used in unison, such as ina duplexed configuration, they are synchronized via a shared line syncsignal 770. Only one print engine 760, selected via the externalmaster/slave pin 771, generates the line sync signal 770 onto the sharedline.

The print engine controller 760 contains a low-speed processor 772 forsynchronizing the page expansion and rendering pipeline, configuring theprinthead 350 via a low-speed serial bus 773, and controlling thestepper motors 675, 676.

In the 8½″ versions of the netpage printer, the two print engines eachprints 30 Letter pages per minute along the long dimension of the page(11″), giving a line rate of 8.8 kHz at 1600 dpi. In the 12″ versions ofthe netpage printer, the two print engines each prints 45 Letter pagesper minute along the short dimension of the page (8½″), giving a linerate of 10.2 kHz. These line rates are well within the operatingfrequency of the Memjet™ printhead, which in the current design exceeds30 kHz.

8 User Interface Diagram Notation

Each application user interface flow is illustrated as a collection ofdocuments linked by command arrows. A command arrow indicates that thetarget document is printed as a result of the user pressing thecorresponding command button on the source page. Some command arrows arelabelled with multiple commands separated by slashes (‘/’s), indicatingthat any one of the specified commands causes the target document to beprinted. Although multiple commands may label the same command arrow,they typically have different side-effects.

In application terms, it is important to distinguish between netpagedocuments and netpage forms. Documents contain printed information, aswell as command buttons which can be pressed by the user to requestfurther information or some other action. Forms, in addition to behavinglike normal documents, also contain input fields which can be filled inby the user. They provide the system with a data input mechanism. It isalso useful to distinguish between documents which contain genericinformation and documents which contain information specific to aparticular interaction between the user and an application. Genericdocuments may be pre-printed publications such as magazines sold at newsstands or advertising posters encountered in public places. Forms mayalso be pre-printed, including, for example, subscription formsencountered in pre-printed publications. They may, of course, also begenerated on-the-fly by a netpage printer in response to user requests.User-specific documents and forms are normally generated on the fly by anetpage printer in response to user requests. FIG. 44 shows a genericdocument 990, a generic form 991, a user-specific document 992, and auser-specific form 993.

Netpages which participate in a user interface flow are furtherdescribed by abstract page layouts. A page layout may contain variouskinds of elements, each of which has a unique style to differentiate itfrom the others. As shown in FIG. 45, these include fixed information994, variable information 995, input fields 996, command buttons 997,draggable commands 998, and text hyperlinks or hypertext links 999.

When a user interface flow is broken up into multiple diagrams, anydocument which is duplicated is shown with dashed outlines in all butthe main diagram which defines it.

8 Commands and Objects

8.1 Dragging and Dropping

The netpage system allows commands and objects to be “dragged anddropped”. This enables a user to instruct the netpage system to executecommands at specific locations or with respect to specific objects on apage, or to place objects at specific locations on a page.

The ability to ‘drag and drop’ commands and objects thus advantageouslyavoids the introduction of modality into the user interface, since adragging action is a single user action.

The dragging action may be performed using the non-marking nib or themarking nib of the pen. If the marking nib is used, the user getsimmediate feedback in the form of the drawn stroke on the page withrespect to the user's command, and printing of the result of thedragging action may be deferred. If the non-marking nib is used the userdoes not get immediate feedback with respect to the command, and theresult of the dragging action typically requires printing uponcompletion of the dragging action.

Dragging may be used to apply an attribute to an object, for example toapply a color from a color palette to the object. Dragging may also beused to drop an object at a location, for example to drop an object froma palette at the location.

Dragging may also be used to apply a command at a location, for exampleto paste a selected object at the location. It may be used to apply acommand to an object, for example to delete the object.

The starting point of the drag stroke is typically the command zone,such as a palette object, and the end point of the drag stroke is thedesired location. The location may be indicative of a desired object, orit may have a meaning in its own right. The graphical representation ofthe draggable command or object is preferably such that it can berecognized by the user as being draggable, as well as beingdistinguishable from something which is normally selected by ‘clicking’,such as a normal hyperlink.

FIG. 46 illustrates the dragging of attributes from a color palette 501and some of the preferred methods by which the drag stroke may identifyan object or object feature. For example, when a user wishes to instructthe computer to execute a command with respect to an object, a dragstroke from a particular color zone of the palette ending inside theobject may be used to designate that object, as is detailed by stroke502 in FIG. 46.

However, when the users wishes to execute a command with respect to theoutline of an object, a drag stroke doubling back so that it crosses theoutline twice may be used to designate the outline feature of theobject, as is detailed by stroke 503 in FIG. 46.

Additionally, when a user wishes to execute a command with respect toone or more objects, a closed loop or lasso at the end of the dragstroke may be used to simulataneously designate multiple objects, as isdetailed by stroke 504 in FIG. 46.

The implementation of the drag-and-drop facility can be effectedentirely by an application. Typically, the application creates a drawingfield large enough to contain any draggable commands (and/or objects) aswell as the target area (i.e. 500 in FIG. 46) into which the commands(and/or objects) will be dragged. The application embeds the drawingfield inside a hyperlinked group 866, and sets the ‘submit delta’attribute of the hyperlink associated with the hyperlinked group.

Whenever the user draws a stroke within the drawing field, theapplication is immediately notified so that it can interpret the strokerelative to the draggable commands and the contents of the target area.Generally, the stroke can be interpreted as normal hand-drawn input ifit does not start in the zone of a draggable command.

The implementation of the drag-and-drop facility may also be effected bythe page server. In this instance, the application may define eachdraggable command (or object) as a draggable hyperlink 506 (asillustrated in FIG. 47). When the page server detects a strokeoriginating within the zone of a draggable hyperlink, it will preferablyactivate the hyperlink and include the name of the target field and thedrag stroke itself in the activation. To assist the application ininterpreting a drag stroke, the page server preferably converts thecoordinates of the drag stroke into coordinates relative to the zone ofthe target field.

An application example of the ‘drag and drop’ mechanism described aboveis in composition of a user's photograph album page. The netpage photomanager application (described in co-pending applications by the presentapplicant filed on May 23, 2000 and identified by docket numbers NPA020and NPA035) is able to serve on demand a photograph album pagecomposition form 520 (FIGS. 52 and 53) to be printed at the user'snetpage printer, which contains a representation of the layout of thecorresponding photograph album page. Each photo on that page may beshown, along with hand-drawn/written annotations, preferably all withcorner handles for enabling the user to change the size of thecorresponding photo or annotation. By draw/dragging on a non-handle areaof a photo or annotation, the user can change the position of the photoor annotation. This is analagous to dragging (and resizing) photo imagesby mouse-controlled cursor on a standard computer display. When the userdraw/drags with the marking nib of the netpage pen, the page is notimmediately updated. Instead, once the user has made all the desiredposition and size changes, he or she can ‘click’ on an <update> buttonto obtain an updated version of the page. When the user draw/drags withthe non-marking nib, the page is immediately updated when the pen tip islifted from the page surface.

The user places a photo in the composition by first selecting aphotograph and then pasting it at the desired position (524 in FIG. 52).For example, a photo may be selected from a user's photogaph folder, andaccess may be granted to other system users by way of an authorizationprotocol, such as by signature recognition. Alternatively a user mayselect a photo by circumscription or lasso on any page showing a photofrom their photo collection (e.g. on a thumbnails page 522 or album page523, shown in FIG. 52), and then draw/drag from a <paste> draw/dragcontrol box (526 in FIG. 53) in the margin of the composition form tothe desired target position in the composition. The page compositionform may be immediately updated. The user adds an annotation to thecomposition by simply drawing or writing with the netpage pen markingnib in a chosen place in the composition. The page is not immediatelyupdated, but the next time the page is updated, the annotation is shownwith handles as mentioned above, allowing the annotation to bere-positioned and re-sized. So long as every drawn stroke begins in aninterstitial area of the composition, it is not interpreted by thesystem as a draw/drag command.

If the user wishes to, say, delete a drawing from the page, he/she maysimply ‘lasso’ it with a stroke of the pen and continue the stroke to a<delete> control box in the margin of the composition form.Alternatively, the application may simply recognise a single continuousstroke from/to the <delete> box to/from any part of the photo image onthe composition form. In either case, the system can be configured toact directly on such a stroke and print an updated composition form(e.g. if a non-marking nib is used), or, alternatively, not to actimmediately (e.g. if a marking nib is used), but to wait until the<update> box is clicked to act to apply the command(s) to the selectedphoto object(s). Once the user is satisfied with a page composition,he/she clicks on a <print page> command box to instruct the printer toproduce a final rendition of the album page.

8.2 Content Selection and Association of Objects

The netpage system provides a mechanism to allow users to select anobject on a printed netpage and submit it to an application, e.g. toassociate the selected object with another object in the netpage system.

In one preferred embodiment, the selection mechanism is effected bycircumscribing the graphical representation of an object using thenetpage pen. The user may then submit the selected object to anapplication by activating a selection hyperlink via the same or anotherprinted netpage.

The registration server maintains a current selection for each pen,describing a region of a page instance from which the selection has beenmade. This description includes the most recent digital ink strokecaptured by way of transmitted signals from the pen relative to thebackground area of the page. Pen strokes are interpreted in anapplication-specific manner once they are submitted to an applicationvia a selection hyperlink activation. When the user ‘clicks’ on aselection hyperlink, the page server obtains the pen's current selectionfrom the registration server and transmits it to the correspondingapplication as part of the selection hyperlink activation, thusassociating the two objects.

When the application receives a selection hyperlink activation, itretrieves the content of the selection from the page server whichmanages the page from which the selection was made. The application maythen retrieve the selection as formatted data, allowing it to interpretthe object in the form of the selected region in an application-specificmanner in relation to the formatted data, or as unformatted data,allowing it to rely on the page server to interpret the selection regionin a meaningful way.

When requesting unformatted data, the application may specify a desiredscope to assist the interpretation of the selected region by the pageserver. Possible scopes include letter, word, phrase, line, paragraphand article. If the page server is unable to interpret the selectionregion according to the desired scope, it may reject the application'srequest for the content of the selection.

The selection content returned by the page server to the application mayinclude field values. Typically however, only field values which havebeen submitted as part of a form submission are included.

An author of a document can assist selection of articles by grouping allthe elements of an article into an article group 507, as shown in FIG.48. If the application specifies an article as the scope in itsselection request, the page server attempts to find an article grouprelated to the selection region.

The protocol for selection hyperlink activation and subsequent selectioncontent retrieval, illustrated diagrammatically in FIG. 51, operates asfollows.

When page server A receives a selection hyperlink ‘click’, it retrieves510 the current selection associated with the pen from the registrationserver. The selection is described by a page ID 511 and a region 512.The page server then constructs a selection hyperlink request 508 (i.e.a specialization of the hyperlink request 934, shown in FIG. 41). Theselection hyperlink request contains the pen's current selection asshown in FIG. 49. The page server then transmits its own server ID, thehyperlink request ID, and the link ID to the application in the usualway. It also sends the pen's current selection to the application. Theapplication uses the page ID in the current selection to identify thepage server managing the page on which the selection was made (ie. pageserver A). It then requests the content of the selection from this pageserver in the desired format 514 and according to the desired scope 513.Page server B uses the server ID and hyperlink request ID supplied bythe application to obtain the selection from original page server A.Page server B obtains the selection from page server A rather than fromthe application in order to ensure that the application does not modifythe selection to obtain information not intended by the user.

As an alternative, page server A could sign the selection sent to theapplication, allowing page server B to easily verify that the selectionsupplied by the application has not been modified. Once page server Bhas the selection, it retrieves the selected page from its database anddetermines the content of the selection according to the application'sdesired format and scope. Finally the page server returns the selectioncontent 515 to the application for application-specific processing.

If the page on which the selection was made was generated by the sameapplication as that handling the selection hyperlink activation, thenthe application has direct access to the page (i.e. the application canretrieve the entire page from the relevant page server by way of thepage ID of the page) and may already have done so before the selectionhyperlink is activated. In this case, the application preferablyinterprets the selection region without reference to the selectioncontent retrieval mechanism.

Selection of an object may of course alternatively be performed using adraggable command. This has an advantage in that a selection stroke canbe distinguished from a normal input stroke wherever the stroke is made.The user may therefore select an object without inadvertently enteringan input stroke into a field. As such, a user is also able to select anobject that resides entirely within a field relatively easily.

The application may define the selection command in the form of aselection page server command 509, as shown in FIG. 50. This may beplaced in a standard location on all netpages, to provide consistentsupport for selection in much the same way that there is consistentsupport for page duplication.

When a selection page server command is activated by a user, the pageserver forwards the corresponding stroke to the registration server tobe recorded as the current selection for the pen. Apart from thisdifference, the selection mechanism operates in the same way aspreviously described.

The photograph collection application referred to above provides anexample of the selection/attachment mechanism described. A user may, forexample, click on a <list frames> button to produce one or more pagescontaining a list of frames available for framing the photo composition(522 in FIG. 52). Frames can, for example, be synthetic or can be basedon photos of actual picture frames. The user adds a frame to a photo inthe composition by first selecting a desired frame on the frame listpage, e.g. by circumscription using the netpage pen, and then pasting itinto the composition (525 in FIG. 52), e.g. by effecting a strokefrom/to the <paste> box to/from the pertinent photo. The systeminteprets this action as a command to associate the selected frame withthe designated photo. The frame list contains a blank frame which theuser can select and paste to remove any frame from the composition. Thepage composition form is updated to show the pasted frame.

As another example, in a netpage e-mail application, clicking onan<attach> button at the bottom of every e-mail composition page effectsattachment of the current selection at the current end of the body ofthe e-mail. The attachment can consist of any object or objects, whichare capable of selection, on any netpage page. The user may have madethis selection from, say, selecting text (eg.word/sentence/paragraph/article) from another netpage page, or selectinga photograph (eg. by circumscription) from a photo collection page. Theentire e-mail may then be reprinted with the attachment included,additional pages being automatically added to the e-mail to accommodatethe attachment.

Conclusion

The present invention has been described with reference to a preferredembodiment and number of specific alternative embodiments. However, itwill be appreciated by those skilled in the relevant fields that anumber of other embodiments, differing from those specificallydescribed, will also fall within the spirit and scope of the presentinvention. Accordingly, it will be understood that the invention is notintended to be limited to the specific embodiments described in thepresent specification, including documents incorporated bycross-reference as appropriate. The scope of the invention is onlylimited by the attached claims.

1. A method for enabling instruction of a computer to perform tasks, themethod including the steps of: providing a user with at least one formprintable on a surface to provide one or more first viewable informationzones relating to one or more available commands and one or more secondviewable information zones relating to one or more objects, the formincluding coded data indicative of an identity of the form and of atleast one reference point of the form; receiving, in a computer system,indicating data from a sensing device operated by the user regarding atleast one of a movement and a position of the sensing device relative tothe surface, at least one of the movement and the position including astroke of part of the sensing device on or relative to said surface;determining, in the computer system and from the indicating data, if thestroke substantially links one or more of said first viewableinformation zones with one or more of said second viewable informationzones, and thereby interpreting the stroke as designating (i) arespective one or more of said available commands and (ii) a respectiveone or more of said objects; and applying in the computer system thedesignated one or more of said available commands to the designated oneor more of said objects, wherein the sensing device comprises: (a) animage sensor adapted to capture images of at least some of the codeddata when the sensing device is placed in an operative position relativeto the surface; and (b) a processor adapted to: (i) identify at leastsome of the coded data from one or more of the captured images; (ii)determine an orientation, within the captured images, of at least someof the coded data; (iii) decode at least some of the coded data; and(iv) generate the indicating data using at least some of the decodedcoded data.
 2. The method of claim 1, wherein the processor is housedwithin the sensing device.
 3. The method of claim 1, wherein theprocessor is adapted to operate at processing speeds ranging from 1instruction per second to 1×10¹² instructions per second.
 4. The methodof claim 3 wherein the processor is adapted to operate at processingspeeds ranging from 10 instructions per second to 1×10⁶ instructions persecond.
 5. The method of claim 1, wherein the image sensor is housedwithin the sensing device.
 6. The method of claim 1, wherein the imagesensor is adapted to capture images at rates ranging from 1 image persecond to 1,000 images per second.
 7. The method of claim 6 wherein theimage sensor is adapted to capture images at rates ranging from 10images per second to 200 images per second.
 8. The method of claim 1,wherein the coded data comprises non-barcode coded data.
 9. The methodof claim 1, wherein said indicating data regarding at least one of themovement and the position of the sensing device relative to the surfaceis generated by the sensing device sensing at least one of the movementand the position of the sensing device relative to the surface using atleast some of the coded data.
 10. The method of claim 1, including thestep of identifying, in the computer system and from said indicatingdata, if the stroke has encircled one or more of said second viewablezones relating to one or more objects, thereby designating said one ormore objects.
 11. The method of claim 1, including the step ofidentifying, in the computer system and from said indicating data, ifthe stroke has intersected one or more of said second viewable zonesrelating to one or more objects, thereby designating said one or moreobjects.
 12. The method of claim 11, at least one of said secondviewable zones having a viewable boundary, and including the step ofidentifying, in the computer system and from said indicating data, ifthe stroke has crossed said boundary more than once, and to apply adifferent one or more of said available commands if such an occurrenceis identified.
 13. The method of claim 1, including the step ofidentifying, in the computer system and from the indicating data, if auser has effected the stroke to designate one or more of said secondviewable zones and extend to intersect with one or more of said firstviewable zones.
 14. The method of claim 1 for designation of a featureof said one or more objects such that said designated one or more of theavailable commands is carried out with respect to that feature.
 15. Themethod of claim 14, wherein said designated feature is a color attributeof said designated one or more objects, and the method includes the stepof setting the value of said color attribute according to the designatedone or more commands.
 16. The method of claim 15, including the step ofproviding the user with a further form printable on a surface includingone or more viewable information zones relating to said designated oneor more of said objects, said one or more zones includingrepresentations of the designated one or more objects rendered accordingto the value of the color attribute.
 17. A system for enablinginstruction of a computer to perform tasks, the system including: atleast one form printable on a surface to provide one or more firstviewable information zones relating to one or more available commandsand one or more second viewable information zones relating to one ormore objects, the form including coded data indicative of an identity ofthe form and of at least one reference point of the form; a computersystem for receiving indicating data from a sensing device operated by auser regarding at least one of a movement and a position of the sensingdevice relative to the surface, at least one of the movement and theposition including a stroke of part of the sensing device on or relativeto said surface, the computer system adapted to determine, from theindicating data received, if the sensing device stroke substantiallylinks one or more of said first viewable information zones with one ormore of said second viewable information zones and thereby designates(i) a respective one or more of said available commands and (ii) arespective one or more of said objects one or more of said availablecommands, the computer system adapted to apply the designated one ormore of said available commands to the designated one or more of saidobjects, wherein the sensing device comprises: (a) an image sensoradapted to capture images of at least some of the coded data when thesensing device is placed in an operative position relative to thesurface; and (b) a processor adapted to: (i) identify at least some ofthe coded data from one or more of the captured images; (ii) determinean orientation, within the captured images, of at least some of thecoded data; (iii) decode at least some of the coded data; and (iv)generate the indicating data using at least some of the decoded codeddata.
 18. The system of claim 17, wherein the processor is housed withinthe sensing device.
 19. The system of claim 17, wherein the processor isadapted to operate at processing speeds ranging from 1 instruction persecond to 1×10¹² instructions per second.
 20. The system of claim 19wherein the processor is adapted to operate at processing speeds rangingfrom 10 instructions per second to 1×10⁶ instructions per second. 21.The system of claim 17, wherein the image sensor is housed within thesensing device.
 22. The system of claim 17, wherein the image sensor isadapted to capture images at rates ranging from 1 image per second to1,000 images per second.
 23. The system of claim 22 wherein the imagesensor is adapted to capture images at rates ranging from 10 images persecond to 200 images per second.
 24. The system of claim 17, wherein thecoded data comprises non-barcode coded data.
 25. The system of claim 17,wherein said indicating data regarding at least one of the movement andthe position of the sensing device relative to the surface is generatedby the sensing device sensing at least one of the movement and theposition of the sensing device relative to the surface using at leastsome of the coded data.
 26. The system of claim 17, the computer systemadapted to identify from said indicating data if the stroke hasencircled one or more of said second viewable zones relating to one ormore objects, thereby designating said one or more objects.
 27. Thesystem of claim 17, the computer system adapted to identify from saidindicating data if the stroke has intersected one or more of said secondviewable zones relating to one or more objects, thereby designating saidone or more objects.
 28. The system of claim 27, at least one of saidsecond viewable zones having a viewable boundary, the computer systemadapted to identify from said indicating data if the stroke has crossedsaid boundary more than once, and to apply a different one or more ofsaid available commands if such an occurrence is identified.
 29. Thesystem of claim 17 including the sensing device.